Composition and method for preparing biocompatible surfaces

ABSTRACT

The invention provides methods and compositions for providing biocompatible surfaces to medical articles. In particular the invention provides biocompatible coatings with heparin activity. In some aspects, the biocompatible coatings of the invention are able to release a bioactive agent. The coatings can be formed using biostable or biodegradable polymeric material and photoreactive groups. The invention also provides methods for improving the quality of bioactive agent-containing coatings by performing pre-irradiation of biocompatible coating compositions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of patent application Ser. No.11/090,655, filed Mar. 25, 2005, now U.S. publication No. 2005/0244453A1and entitled COMPOSITION AND METHOD FOR PREPARING BIOCOMPATIBLESURFACES, which claims the benefit of U.S. Provisional Application No.60/556,634, filed on Mar. 26, 2004, and entitled PROCESS AND SYSTEMS FORBIOCOMPATIBLE SURFACES; U.S. Provisional Application No. 60/568,021,filed on May 3, 2004, and entitled COMPOSITION AND METHOD FOR PREPARINGBIOCOMPATIBLE SURFACES; U.S. Provisional Application No. 60/640,602,filed on Dec. 31, 2004 and entitled COMPOSITION AND METHOD FOR PREPARINGSURFACES WITH BIOCOMPATIBILITY; and U.S. Provisional Application No.60/567,915, filed on May 3, 2004, and entitled DRUG RELEASE COATING WITHBLOOD COMPATIBLE POLYMERIC TOPCOAT, which Applications are incorporatedherein by reference in their entirety.

FIELD OF THE INVENTION

The invention relates to preparation of biocompatible surfaces. Moreparticularly, the invention relates to preparing biocompatible surfacesby disposing a composition that includes a biocompatible agent on asurface of a medical article. In addition, the invention relates tocompositions that include a biocompatible agent and coating compoundsthat have incorporated the biocompatible agent.

BACKGROUND OF THE INVENTION

Recently, the use of drug-eluting stents (DES) in percutaneous coronaryinterventions has received much attention. DES are medical devices thatpresent or release bioactive agent into their surroundings (for example,luminal walls or coronary arteries). Generally speaking, bioactive agentcan be coupled to the surface of a medical device by surfacemodification, embedded and released from within polymer materials(matrix-type), or surrounded by and released through a carrier(reservoir-type). The polymer materials in such applications shouldoptimally act as a biologically inert barrier and not induce furtherinflammation within the body. However, the molecular weight, porosity ofthe polymer, a greater percentage of coating exposed on the medicaldevice, and the thickness of the polymer coating can contribute toadverse reactions to the medical device.

Improved compatibility with blood is a desired feature for a variety ofmedical devices that contact blood during clinical use. The materialsused for manufacture of medical devices are not inherently compatiblewith blood and its components, and the response of blood to a foreignmaterial can be aggressive, resulting in surface induced thrombus (clot)formation. This foreign body response can in turn impair or disable thefunction of the device and, most importantly, threaten patient health.It is often desirable to modify the surface of medical devices, such asDES, to provide a biocompatible surface, to minimize or avoid suchadverse foreign body responses.

As used herein, a surface of a medical article is characterized as“biocompatible” if it is capable of functioning or existing in contactwith biological fluid and/or tissue of a living organism with a netbeneficial effect on the living organism. Long-term biocompatibility isdesired for the purpose of reducing disturbance of a host organism. Oneapproach to improved biocompatibility for medical device surfaces is toattach various biomolecules such as antithrombogenic agents,anti-restenotic agents, cell attachment proteins, growth factors, andthe like, to the surface of the device. For example, antithrombogenicagents can reduce the generation of substances as part of the clottingcascade, antirestenotic agents can reduce generation of aggressive scartissue growth around the device, while cell attachment proteins cancontribute to the growth of a layer of endothelial cells around thedevice.

Several benefits can be provided by biocompatible medical devicesurfaces. For example, such surfaces can increase patient safety,improve device performance, reduce adherence of blood components,inhibit blood clotting, keep device surfaces free of cellular debris,and/or extend the useable lifetime of the device.

One biomolecule that has been utilized to improve biocompatibility ofmedical device surfaces is heparin. Heparin is a pharmaceutical that hasbeen used clinically for decades as an intravenous anticoagulant totreat inherent clotting disorders and to prevent blood clot formationduring surgery and interventional procedures. Heparin molecules arepolysaccharides with a unique chemical structure that gives themspecific biological activity. When heparin is immobilized onto thesurface of a medical device material, it can improve the performance ofthe material when in contact with blood in several ways: 1) it canprovide local catalytic activity to inhibit several enzymes critical tothe formation of fibrin (which holds thrombi together); 2) it can reducethe adsorption of blood proteins, many of which lead to undesirablereactions on the device surface; and 3) it can reduce the adhesion andactivation of platelets, which are a primary component of thrombus.

In addition to heparin, other biomolecules that can be provided on amedical device to improve biocompatibility include extracellular matrix(ECM) proteins or ECM peptides derived from these proteins. Surfacesmodified with appropriate proteins or peptides are less likely to berecognized as foreign than the original device surface and will promotethe attachment and overgrowth of specific desirable cell types.

The preparation of biocompatible surfaces, however, can be challenging.This is particularly the case when attempting to providebiocompatibility to devices that also have other properties, such asDES. Materials that are used to form these coating may not be inherentlycompatible with each other, thereby making it difficult to form acoating that is both biocompatible and that has drug-releasingproperties.

In addition, treatments that are used to form coatings can in some casesdamage the bioactive agent and therefore reduce the overalleffectiveness of the coated article. This may be the case whenirradiation is used to form all or part of the coating. Irradiationsources can be useful for activating components of a coating compositionto form the coating, but can also lack the specificity and thereforecause degradation of the bioactive agent that is present in the coating.

Another problem relates to the release of bioactive agent, as somematerials release the bioactive agent immediately upon contact withtissue; therefore the bioactive agent is not present for an amount oftime sufficient to provide a beneficial effect.

SUMMARY OF THE INVENTION

The invention relates to methods and systems for providing biocompatiblesurfaces to medical devices. According to the invention, a biocompatibleagent is coupled to the polymeric material to provide a biocompatiblesurface of the medical article.

In one aspect, the invention provides methods of coupling abiocompatible agent to a surface of a medical article, the methodsincluding the following steps: (a) providing a polymeric material on asurface of a medical article, the polymeric material comprising one ormore bioactive agents; and (b) providing biocompatible agent to thepolymeric material under conditions sufficient to couple thebiocompatible agent to the polymeric material, wherein coupling of thebiocompatible agent with the polymeric material is accomplished byactivating photoreactive groups provided by the polymeric material, thebiocompatible agent, or both the polymeric material and thebiocompatible material.

Optionally, the biocompatible agent can be premixed with a secondpolymeric material prior to application of the biocompatible agent tothe polymeric material. The second polymeric material can be the same ordifferent from the polymeric material provided on the surface of themedical article. That is, the biocompatible agent can be premixed withand coupled to a polymeric material prior to application on the surface.

In some embodiments, the biocompatible agent includes one or morephotoreactive groups, and coupling of the biocompatible agent to thepolymeric material is accomplished by activating one or more of thephotoreactive groups of the biocompatible agent. That is, for example,the biocompatible agent having photoreactive groups is premixed andcoupled to the polymeric material via the photoreactive groups prior toapplication on the surface.

In other aspects of the invention, the polymeric material includes oneor more photoreactive groups, and coupling of the biocompatible agent tothe polymeric material is accomplished by activating one or more of thephotoreactive groups of the polymeric material. That is, for example, apolymeric material having photoreactive groups is premixed and coupledto the biocompatible agent via the photoreactive groups prior toapplication.

A composition that includes the polymeric material, biocompatible agent,and photoreactive groups can be utilized in a coating in a number ofdifferent ways. In some aspects, this composition is disposed over abioactive-agent containing coated layer. In other aspects a bioactiveagent is mixed into the composition and disposed on the surface of adevice. In yet other aspects the composition can be disposed on anarticle to form a coating that does not include a bioactive agent. Inany of these aspects the composition can be pre-treated to activate thephotoreactive groups to couple the biocompatible agent to the polymericmaterial, before the composition is disposed.

In one aspect, the invention provides methods of providing abiocompatible coating to a surface of a medical article. The methodscomprise the steps of (a) providing a coating composition comprising (i)a polymeric material, (ii) a biocompatible agent, and (iii) aphotoreactive moiety, wherein the photoreactive moiety is pendent from(i), pendent from (ii), independent, or combinations thereof, (b)disposing the coating composition on the surface of the medical article;and (c) treating the coating composition to activate the photoreactivemoiety. The photoreactive moiety can be activated to couple thepolymeric material to the biocompatible agent. In some aspects it ispreferable that the photoreactive moiety is pendent from thebiocompatible agent.

In many aspects of the invention the step of treating the coatingcomposition to activate the photoreactive moiety is performed before thestep of disposing the coating composition on the surface of the medicalarticle. In other aspects, the photoreactive moiety can be activatedafter or during the step of disposing. In yet other aspects activationof photoreactive moieties can be performed more than one time during themethod. For example, the coating composition can be treated with UVirradiation before the step of disposing and after the composition iscoated onto the surface. If a step of treating is performed more thanone time it is preferred that there are photoreactive moieties capableof being activated present in the coating composition after thecomposition has been treated.

The polymeric material of the biocompatible coating compositionpreferably includes a polymer that has good adhesive properties (forexample, a polymer that is “sticky”). This type of polymer, hereinreferred to as an “adherent polymer”, can, in some embodiments, bedeposited and stick to a surface without providing substantialadditional treatment to make the polymer adhere. Many polymers havingadherent properties are known in the art. Such a polymer with adherentproperties can be synthetic or natural. Suitable polymers and copolymersinclude acrylate, methacrylate, ethylene glycol, vinyl pyrrolidinone,and glucose monomeric units.

In some aspects the adherent polymer preferably includespoly(alkyl(meth)acrylates) and poly(aromatic (meth)acrylates), where“(meth)” will be understood by those skilled in the art to include suchmolecules in either the acrylic and/or methacrylic form (correspondingto the acrylates and/or methacrylates, respectively).

In yet other aspects the polymeric material is biodegradable. Suitablebiodegradable polymers include, for example, polylactic acid andpolyglycolic acid.

In some aspects, the polymeric material of the biocompatible coatingcomposition is able to incorporate and controllably release or present abioactive agent. The property of being able to incorporate andcontrollably release a bioactive agent can be provided by one or morepolymers, or can be provided by a mixture of polymers. For example amixture of an adherent polymer and a polymer that is different than thatadherent polymer can be used. For example, in some preferred aspects,the coating composition has a mixture of polymers includingpoly(butyl)methacrylate and poly(ethylene-co-vinyl acetate).

In other aspects, the polymeric material of the coating compositionincludes polymers such as Parylene™ and ethylene vinyl alcohol.

In some aspects the biocompatible agent provides a hemocompatible (bloodcompatible) surface to the medical article. For example, a medicalarticle with a hemocompatible coating can reduce effects that mayassociated with placing a foreign object in contact with bloodcomponents, such as the formation of thrombus or emboli (blood clotsthat release and travel downstream.

The biocompatible agent can be a larger molecule, such as a polymer thatincludes amino acid or saccharide monomeric units; or a smaller moleculethat is non-polymeric, for example, a small synthetically prepared ornaturally derived molecule.

In some aspects the biocompatible agent is a polymer, for example, ahydrophilic polymer having biocompatible properties (herein referred toas a “hydrophilic biocompatible polymer”). Preferably, the hydrophilicpolymer has hemocompatible properties, meaning that it promotescompatibility with blood components by minimizing events that maycompromise the function of the device, such as thrombus formation nearthe coated surface.

A hydrophilic biocompatible polymer can be a natural polymer, or can bederived from a natural polymer. The hydrophilic biocompatible polymercan also include charged groups, such as sulfonate groups. In someaspects the hydrophilic polymer is a polysaccharide. According to theinvention, particularly useful polysaccharides can be selected frommucopolysaccharides such as heparin, hyaluronic acid, chondroitin,keratan, and dermatan. In preferred embodiments the biocompatiblepolymer is heparin. In some preferred embodiments, the biocompatiblepolymer is selected from heparin, heparin derivatives, sodium heparin,and low molecular weight heparin. As used herein “heparin” is meant toencompass all forms of heparin, including derivatives and differentmolecular weight preparations of heparin.

It has been discovered that a bioactive agent releasing coating that hasexcellent heparin activity can be formed according to the inventivemethods described herein. In determining the heparin activity, an assaycan be performed and compared to results of an assay performed usingheparin standards.

Therefore, in some aspects, the invention provides a medical articlehaving a bioactive agent-releasing coating having heparin activity of 10mU/cm² or greater. Bioactive agent-releasing coatings were also preparedhaving a heparin activity of 15 mU/cm² or greater, 20 mU/cm² or greater,25 mU/cm² or greater, 30 mU/cm² or greater, 35 mU/cm² or greater, 40mU/cm² or greater, 45 mU/cm² or greater, and 50 mU/cm² or greater.Biocompatible coatings having these activities can also be formedwithout a bioactive agent being present in the coating.

In one aspect, the photoreactive moiety present in the coatingcomposition is pendent from the biocompatible agent. One example of abiocompatible agent having a pendent photoreactive moiety isphoto-heparin, as described herein. Another example is photocollagen, asdescribed herein. The pendent photoreactive moiety is activatable,meaning that it can be activated to form a radical species that canextract hydrogen from a target moiety, and thereby form a covalent bondbetween, for example, the biocompatible agent and a target moiety. Forexample, the photoreactive group can be activated to couple thebiocompatible agent to the polymeric material.

The invention also provides a coating compound formed by treating acoating composition that comprises an adherent polymer and abiocompatible agent, wherein the adherent polymer and the biocompatibleagent are coupled via a photoreactive moiety. In one particular aspect,the invention provides poly(butyl)methacrylate-heparin and/orpoly(butyl)methacrylate-collagen adducts, wherein thepoly(butyl)methacrylate is coupled to the heparin or the collagen via aphotoreactive moiety.

In another aspect, the polymeric material can be coupled to thebiocompatible agent using a bifunctional reagent, that includes aphotoreactive group, and another latent reactive group, such as athermally reactive group. In this aspect, the latent reactive group isreactive with a portion of the biocompatible agent, and thephotoreactive group is reactive with the polymeric material. Suitablethermally reactive groups include NOS groups (N-oxysuccinimide). Anexemplary method of coupling involves reacting a NOS groups of abifunctional reagent with an amine group of heparin, and activating thephotoreactive group to bind a polymeric material such aspoly(butyl(meth)acrylate).

In another aspect of the invention, a miscibility enhancer is added tothe biocompatible coating composition. A miscibility enhancer can beused to improve the homogeneity of the polymeric material and thebiocompatible agent in the coating composition and improve the overallcoating composition. According to the invention, the miscibilityenhancer can be used improve the coupling of the biocompatible agent tothe polymer, for example, an adherent polymer.

The miscibility enhancer can be a compound that can improve thecompatibility of the adherent polymer with the biocompatible agent. Forexample, in some aspects the adherent polymer is hydrophobic, while thebiocompatible agent is hydrophilic. In some cases, for example, anamphoteric agent can be used as the miscibility enhancer.

The miscibility enhancer can be selected from the group consisting ofpolyvinylpyrrolidinone (PVP), polyethyleneglycol (PEG), PEG sulfonates,fatty quaternary amines, fatty sulfonates, fatty acids, dextran,dextrin, and cyclodextrin. The miscibility enhancer can also includependant photoreactive groups.

Therefore, in another aspect, the invention provides another method forproviding a biocompatible surface of a medical device. The methodcomprises the steps of (a) providing a coating composition comprising(i) an adherent polymer, (ii) miscibility enhancer, (iii) abiocompatible agent, and (iv) a photoreactive moiety, and wherein thephotoreactive moiety is pendent from (i), pendent from (ii), pendentfrom (iii), independent, or combinations thereof; (b) disposing thecoating composition on the surface of the medical article; and (c)treating the coating composition to activate the photoreactive group.

In some aspects the biocompatible layer includes at least threecomponents and photoreactive groups. In some aspects the biocompatiblelayer includes at least three polymers. One of the three polymers can bea hydrophobic polymer (such as a poly(alkyl(meth)acrylate), another is abiocompatible polymer (such as heparin), and the other is apoly(vinylpyrrolidone) polymer. In the biocompatible coated layer, thephotoreactive groups have been activated either prior to the coatingcomposition being deposited on the article, after the coatingcomposition has been deposited on the article, or both before and afterthe coating composition has been deposited on the article.

In a preferred aspect the biocompatible coated layer consists of (i) ahydrophobic polymer, preferably a poly(alkyl(meth)acrylate) such aspBMA, present in the layer in an amount by weight in the range of 75% to90%; (ii) hydrophilic biocompatible polymer such as heparin present inthe layer in an amount by weight in the range of 5% to 15%; and (iii) aPVP polymer present in the layer in an amount by weight in the range of5% to 15%.

In some embodiments, the photoreactive moiety is pendent from thebiocompatible agent. Upon activation of the photoreactive groups thebiocompatible agent can be coupled to another component, for example,the polymeric material. The coupling can be performed in one step, forexample prior to disposing the composition on the medical article, or inmore than one step, for example, before and after (and/or during) thestep of disposing.

In yet other embodiments the photoreactive moiety is independent of thebiocompatible agent and the polymeric material. For example, thephotoreactive moiety is a molecule having at least one photoreactivegroup that is able to couple the biocompatible agent to the polymericmaterial when activated. One example is a crosslinking agent thatincludes two or more photoreactive groups.

In some cases the method of providing a biocompatible coating to asurface of a medical article includes a step of providing a medicalarticle having a bioactive agent-releasing layer. While, in some cases,a medical article having a bioactive agent-releasing layer can beobtained, in other cases the method can include a step of forming abioactive agent-releasing layer on the surface of a medical article.

The bioactive agent can be released from or presented by the coatingonce the coating is formed on the medical article and implanted in apatient. In some embodiments, the coating composition can include morethan one bioactive agent, wherein each of the bioactive agents can beindependently selected depending upon the desired therapeuticapplication of the invention.

Accordingly, the invention also provides a medical article having abiocompatible, bioactive agent releasing coating, the coating comprisinga bioactive agent-releasing layer and a biocompatible layer. The term“bioactive agent-releasing layer” refers to the coated layer that isprepared from a coating composition that includes a bioactive agentintended to be released from the coating. It is understood that when thecoating is formed, and/or after the coating is formed, the bioactiveagent can become present in layers other than the bioactiveagent-releasing layer. The bioactive agent-releasing layer is formedbetween biocompatible layer (i.e., the coated layer that includes thebiocompatible agent) and the surface of the article. The bioactiveagent-releasing layer can also include a polymeric material, such as ahydrophobic polymer. As indicated, the composition that includes thebiocompatible agent, polymeric material, and the photoreactive groupscan be irradiated prior to disposing the composition on thebioactive-agent releasing layer.

The coated medical article can function to release a bioactive agent ina localized and controlled manner from the surface of the article, whenthe article is placed in vivo, such as by implantation or delivery to atarget region in the body. To be released in a localized and controlledmanner, the bioactive agent, initially being present in the bioactiveagent-releasing layer, can pass through the biocompatible layer beforethe bioactive agent is released in a localized manner. Optionally, thebioactive agent can pass through any other coated layer that is betweenthe bioactive agent-containing layer and the outermost layer (i.e., thelayer that is in contact with a physiological environment) of the coatedarticle that may be present in the coating. The bioactive agent thenbecomes locally therapeutically available when it reaches the interfaceof the coating and body tissue or fluid.

Therefore, in some aspects of the invention, a method for preparing amedical article having a bioactive agent-releasing coating with heparinactivity can include the steps of providing a medical article having afirst coated layer comprising a bioactive agent; irradiating acomposition comprising heparin, photoreactive groups, and polymericmaterial to activate the photoreactive groups; and then after theirradiation step, disposing the irradiated composition on the firstcoated layer.

In some aspects the bioactive agent-releasing layer can include ahydrophobic polymer selected from the group consisting ofpoly(meth)acrylates. In a preferred aspect the bioactive agent-releasinglayer includes a poly(alkyl(meth)acrylates) having a short chain alkylgroup, such as those in the range of C₂-C₅, including propyl (C₃), andmost preferably butyl (C₄). Most preferably the bioactiveagent-releasing layer includes poly(butyl(meth)acrylate) (pBMA).

In another aspect the bioactive agent-releasing layer includes a firstpolymer which is hydrophobic and a second polymer that is different thanthe first polymer. The second polymer can be a polymer that improves orchanges one or more properties of the bioactive agent-releasing layer.For example a second polymer can improve the pliability of the firstlayer, or can change the characteristics of the release of the bioactiveagent from the bioactive agent-releasing layer. Second polymers caninclude polymers having ethylene and vinyl acetate monomeric units, andpreferably ethylene and vinyl acetate copolymers (poly(ethylene-co-vinylacetate); pEVA). In some preferred embodiments, the bioactiveagent-releasing layer includes a blend of pBMA and pEVA polymers.

The invention also contemplates medical articles having a biocompatiblecoating that does not include a bioactive agent-releasing layer. Becausethe inventive biocompatible coating compositions described herein haveoutstanding utility, coatings can be formed wherein drug release is nota required feature, although biocompatibility is. Therefore, in someaspects, the invention provides a medical article having a biocompatiblecoated layer, and optionally other layers that do not include abioactive agent.

According to the invention, at least a portion of the surface of themedical article is coated with the coating composition. In someembodiments, the entire surface of the medical article can be coatedwith the coating composition. The amount of the surface area providedwith the polymeric material can be determined according to such factorsas the medical device to be utilized, the application of the device, thebioactive agent to be utilized with the polymeric material, and the likefactors.

The coating composition described herein can be deposited on the medicalarticle utilizing any known application technique. In some preferredaspects, the coating composition is applied by spray coating. In otheraspects, the coating composition is deposited on the medical article bydip coating the medical article in the coating composition. The coatingcomposition can be treated before, after, or before and after thecoating is deposited on the medical article.

In other aspects, the invention provides a medical article having acoating (“a coated composition”), the coating comprising a polymericmaterial, a biocompatible agent, and a photoreactive and/or photoreactedmoiety. In preferred aspects the components of the coating compositionare deposited on the surface in a single application of coatingmaterial. The photoreactive moiety can couple the biocompatible agent toat least the polymeric material. The coating includes a layer whereinboth the polymeric material and the biocompatible agent are present,that is, the coating includes a layer of material wherein thebiocompatible agent is dispersed in and/or coupled to the polymericmaterial via the photoreactive moiety. Advantageously, after the coatingcomposition has been disposed on the surface of the medical article, thebiocompatible agent is arranged in the coated composition in such amanner as to provide excellent biocompatible surface properties.

The invention generally relates to methods and systems for providing abiocompatible coating to a medical article. In some aspects, theinvention relates to forming a biocompatible coating on a medicalarticle, the medical article having another coated layer that includesand than can release a bioactive agent. According to the invention, thebiocompatible layer in conjunction with the bioactive agent-releasinglayer form a coating that has excellent biocompatibility and bioactiveagent-releasing properties.

According to the invention, the biocompatible coating can be formedusing an improved coating composition that includes polymeric componentsand photoreactive moieties. Some of the compositions described hereininclude heparin and can be used to form coatings that have heparinactivity. For example, the methods and compositions are used to providea biocompatible coated layer having heparin activity to a medicalarticle having a formed bioactive agent-releasing coated layer.

The biocompatible layer improves the function of the medical article inmany ways. For example, the biocompatible layer can substantially reducethe accumulation of clotting components on the surface of the article.This reduction means that the release of the bioactive agent will not becompromised by any sort of blockage on the surface of the device ascaused by the clotting components. In addition, the biocompatible coatedlayer can also improve the mechanical function of the device, as thesesimilar components will not accumulate on the device and compromise itsmechanical function. In this manner, the coating has excellentanti-adherence properties. These anti-adherence properties are thought,at least in part, to be provided by the combination of the polymericmaterials in the biocompatible layer (for example, the hydrophilicbiocompatible polymer and the PVP polymer).

The composition and methods of the invention can provide one or moredistinct advantages for the preparation of biocompatible, bioactiveagent-releasing medical articles. While the preparation of a surface ofa medical article that has both drug-releasing and biocompatibleproperties can be challenging from a number or perspectives, theinvention provides a way to prepare these types of coated surfaceswithout compromising properties that are provided by the individualcomponents and which can be important for in vivo use. Illustrativeadvantages that can be observed with the inventive compositions andmethods will now be discussed. It is understood that any one or more ofthese may be demonstrated by the invention.

One advantage relates to the ability to efficiently and cost effectivelyprovide a coated layer having biocompatibility to a medical article, themedical article also having a bioactive agent-releasing coated layer.This can be seen, in some aspects, by the ability to form a bioactiveagent-releasing, biocompatible coating on the surface of a medicalarticle in minimal number of steps. In some cases, and in its simplestform, a coating can be formed by applying the biocompatible coatingcomposition onto a medical article having one, or more then one,pre-formed coated layer(s) that includes a bioactive agent. In othercases, the coating can be formed in a method that includes two steps,that is, a coating is formed by disposing a first composition thatincludes a bioactive agent, and subsequently a second composition thatincludes a biocompatible polymer. The methods described herein greatlyreduce the throughput time for the fabrication of medical articleshaving biocompatible and bioactive agent-releasing properties. This, inturn, can result in a substantial cost savings for the preparation ofthese medical articles, as many reagents and steps that might typicallybe attempted in fabrication of these coated medical articles are notnecessarily required.

Another advantage of the present invention is that a biocompatiblecoating can be formed on the surface of a bioactive agent-releasinglayer without significantly compromising the bioactive agent-releasingproperties of the coating. For example, a coating with heparin activitycan be formed on a medical article having a drug-releasing layer withoutsignificantly altering the drug releasing profile of the coating. Also,according to the invention, the presence of a bioactive agent-releasinglayer does not compromise the formation or properties of a coated layerhaving biocompatible properties, such as heparin activity. Such resultsare seen because the present invention overcomes typical problems thatcan be encountered when multiple layers of coated materials are providedto a surface in order to provide a coating having more than oneproperty. Therefore, in this regard, the properties of the inventivecoatings described herein with regard to biocompatibility (e.g., heparinactivity) and bioactive agent release are particularly surprising, asone would not expect that the biocompatible and drug-releasingproperties would be maintained at levels that were achieved bypreparation of these coatings not in combination. In other words, whileit was expected that the combination of coated layers would lead to adecrease in the activity of each layer, this expectation, in fact, wasnot realized based on the results seen when bioactivity and drug releasewere tested on the inventive coatings described herein.

Yet another advantage of preferred embodiments of the invention is thatit can provide methods for the preparation of biocompatible coatingcompositions that include polymeric materials which are typicallydifficult to combine and/or do not form a coated layer that has suitableactivity or physical properties. Accordingly, the invention alsoprovides methods for forming a coated layer on the surface of a medicalarticle that includes combinations of these types of polymericmaterials. The present invention overcomes problems, specifically, withpreparing a coating composition that includes a hydrophilicbiocompatible polymer and a hydrophobic polymeric material. The presentinvention not only overcomes challenges posed with the preparation ofthese coating compositions, but also challenges associated with forminga coating on the surface of an article, wherein the polymeric componentsare well dispersed (or mixed) in the coating and have properties thatare reflected by the presence of both the hydrophilic biocompatiblepolymer and a hydrophobic polymeric material.

Yet another advantage of preferred embodiments of the invention is seenfrom results showing that the biocompatible bioactive-agent releasingcoating has excellent durability. Test results demonstrate that thecoating is durable and retains good biocompatible properties after thearticle has been subject to physical stresses. Such physical stressesmay otherwise cause inferior (unacceptable) coatings to crack ordelaminate from the surface of the device, thereby compromising thefunction of the coating by reducing, for example, biocompatibleactivity. Physical stresses can be encountered at one or more pointsduring processes involving use of the article, including insertion ofthe article into the body.

Excellent biocompatible properties were also observed after the coatedarticle was placed in a biochemical environment simulating thebiochemical stresses that are encountered when the coated article isplaced in vivo. It is generally desirable to form coatings that notdegrade and that are not fouled by the presence of body fluids such asblood. Rather, it is desirable that the coatings display prolongedbiocompatible activity in conjunction with the function of the device.Results of analysis of the inventive coatings described hereindemonstrate that the coated articles are resistant to losingbiocompatible properties even after the coated articles have been placedin conditions that simulate a physiological environment for an extendedperiod of time.

Still yet another advantage of the invention is the ability to pre-treatcomponents that are associated with the biocompatible coated layer,prior to disposing the biocompatible coating composition on an articlehaving a bioactive agent coated layer. “Pre-treating” refers to applyinga source of energy, such as actinic radiation (e.g., UV irradiation),that activates the photoreactive groups that are present in thebiocompatible coating composition. These photoreactive groups areactivated as a step in the process of forming the biocompatible layer,and generally serve to couple the polymeric agents that are present inthis composition. While the step of applying a source of energy to thebiocompatible composition can be performed before or after thecomposition is coated on the article, in many instances it is desirableto perform this step prior to disposing the composition. For example, aclear benefit of pre-treatment would be avoiding irradiating the articlehaving a bioactive coated layer that includes a bioactive agent that issensitive and, for example, can become inactive (for example, bydegradation), upon exposure to this irradiation. Advantageously, thebiocompatible coating composition that was pre-treated and disposed onan article having a bioactive agent-containing layer was able to form alayer having excellent biocompatible properties and that also providedan overall coating that demonstrated excellent bioactive agent releaseprofiles. Therefore, this pre-treatment method preserves the quality ofbioactive agents.

The invention will now be described in more detail.

DETAILED DESCRIPTION

The embodiments of the present invention described herein are notintended to be exhaustive or to limit the invention to the precise formsdisclosed in the following detailed description. Rather, the embodimentsare chosen and described so that others skilled in the art canappreciate and understand the principles and practices of the presentinvention.

All publications and patents mentioned herein are hereby incorporated byreference. The publications and patents disclosed herein are providedsolely for their disclosure. Nothing herein is to be construed as anadmission that the inventors are not entitled to antedate anypublication and/or patent, including any publication and/or patent citedherein.

The present invention is directed to methods for preparing abiocompatible surface on a medical article. The biocompatible surfacethus enhances the ability of the medical article to function or exist incontact with biological fluid and/or tissue of a living organism with anet beneficial effect on the living organism. In preferred embodiments,the biocompatible surface can provide one or more advantages, such asincreased patient safety, improved device performance, reduced adherenceof unwanted blood components, inhibition of blood clotting, maintenanceof device surfaces free of cellular debris, and/or extension of theuseable lifetime of the device.

The methods described herein are particularly suitable for preparing abiocompatible surface on a medical article. In one embodiment, thebiocompatible surface can be prepared by disposing a coating compositionthat includes a polymeric material, a biocompatible agent, and aphotoreactive moiety on a substrate. In preferred embodiments thephotoreactive moiety is pendent from the biocompatible agent. In anotherembodiment, a biocompatible surface can be prepared by disposing acoating composition that includes a polymeric material, a biocompatibleagent, a miscibility enhancer, and a photoreactive moiety. The polymericmaterial preferably includes an adherent polymer that is capable ofadhering to a surface.

A bioactive agent can also be included in the coating composition. Thepresence of one or more bioactive agents in a coating that is on thesurface of the medical article may render the device surface sensitiveto irradiation with light, since certain wavelengths can inactivatebioactive agents.

In some aspects, the invention provides a multi-component coating formedon the surface of a medical article has properties including being (i)bioactive-agent releasing and (ii) biocompatible. Generally, the coatingincludes at least two coated layers, (i) one layer being a bioactiveagent-releasing layer that includes a polymeric material having abioactive agent, and (ii) another layer being a biocompatible layer thatincludes two or more polymeric materials (one of them being abiocompatible polymer) and photoreactive groups. The bioactiveagent-releasing layer is formed between the biocompatible layer and thesurface of the article. The coating can consist of these two layers, orcan optionally include other layers.

In forming the biocompatible coating, the coating composition thatincludes the biocompatible polymer and photoreactive groups isirradiated. The coating composition can be irradiated to activate thephotoreactive groups before or after the coating composition is disposedon the surface, or both before and after. The exact method ofirradiation may depend on the type and/or amount of photoreactive groupthat is associated with the coating on the surface of the article.

In some embodiments, the photoreactive moiety is pendent from thebiocompatible polymer. For example, at least one photoreactive group iscovalently bonded to the biocompatible polymer. Upon activation of thephotoreactive groups the biocompatible polymer can be coupled to anothercomponent, for example, the polymeric material. The coupling can beperformed in one step, for example prior to disposing the composition onthe medical article, or in more than one step, for example, before andafter (and/or during) the step of disposing. In some embodiments, afilter is utilized in connection with the step treating, which caninvolve the activation of the one or more photoreactive groups. Inembodiments wherein a bioactive agent is included in the coatingcomposition, the one or more photoreactive groups are activated byproviding light having a wavelength selected in a range to activate thephotoreactive groups and minimize inactivation of bioactive agent in thepolymeric material.

The methods described herein are also particularly suitable forpreparing a biocompatible, bioactive agent-releasing coating on amedical article. In some preferred aspects the biocompatible coatingcomposition is disposed on a medical article having a bioactiveagent-releasing layer. The bioactive agent releasing layer can include abioactive agent and a hydrophobic polymer, for example apoly(alkyl(meth)acrylate) such as pBMA.

The invention also relates to methods for providing a biocompatiblesurface to an implantable medical article. The implantable medicalarticle can be, for example, a stent or a synthetic graft having astructure adapted for the introduction into a patient. In someembodiments the device is coated with coating composition that includesa polymeric material and one or more bioactive agents for delivery of adrug or pharmaceutical substance to tissues adjacent the site ofimplantation. In some cases reference is made to a stent having adrug-containing polymeric matrix on its surface (also referred to as adrug-eluting stent, or “DES”) and having a biocompatible surface. Themethods and compositions of the invention in connection with DES havebeen chosen because these devices are designed to reside in the body forextended periods of time, thus increasing risk of adverse body reactionsto the device. Further, in terms of lowering the risk while providing asuperior device, the advantages of this invention can be clearlypresented. However, it is understood that the methods disclosed areapplicable to any medical articles where attachment of a biocompatibleagent are desirable, and are not limited to the particular medicalarticle surfaces described herein.

In some embodiments, the invention provides methods of providingbiocompatible surfaces to medical devices that carry a polymericmaterial that can have bioactive agents associated therewith. Theinvention can be utilized in connection with medical devices having avariety of biomaterial surfaces. Preferred biomaterials include thoseformed of synthetic polymers, including oligomers, homopolymers, andcopolymers resulting from either addition or condensationpolymerizations. Examples of suitable addition polymers include, but arenot limited to, acrylics such as those polymerized from methyl acrylate,methyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate,acrylic acid, methacrylic acid, glyceryl acrylate, glycerylmethacrylate, methacrylamide, and acrylamide; vinyls such as ethylene,propylene, vinyl chloride, vinyl acetate, vinyl pyrrolidone, andvinylidene difluoride. Examples of condensation polymers include, butare not limited to, nylons such as polycaprolactam, polylauryl lactam,polyhexamethylene adipamide, and polyhexamethylene dodecanediamide, andalso polyurethanes, polycarbonates, polyamides, polysulfones,poly(ethylene terephthalate), polylactic acid, polyglycolic acid,polydimethylsiloxanes, and polyetherketone.

Certain natural materials are also suitable biomaterials, includinghuman tissue such as bone, cartilage, skin and teeth; and other organicmaterials such as wood, cellulose, compressed carbon, and rubber. Othersuitable biomaterials include metals and ceramics. The metals include,but are not limited to, titanium, Nitinol, stainless steel, tantalum,and cobalt chromium. A second class of metals includes the noble metalssuch as gold, silver, copper, and platinum uridium. Alloys of metals aresuitable for biomaterials as well. The ceramics include, but are notlimited to, silicon nitride, silicon carbide, zirconia, and alumina, aswell as glass, silica, and sapphire.

Combinations of ceramics and metals are another class of biomaterials.Another class of biomaterials is fibrous or porous in nature. Thesurface of such biomaterials can be pretreated (for example, with aParylene™-containing coating composition) in order to alter the surfaceproperties of the biomaterial, when desired.

Biomaterials can be used to fabricate a variety of implantable devices.The medical device can be any device that is introduced temporarily orpermanently into a mammal for the prophylaxis or treatment of a medicalcondition. These devices include any that are introduced subcutaneously,percutaneously or surgically to rest within an organ, tissue, or lumenof an organ, such as arteries, veins, ventricles, or atria of the heart.

Compositions of this invention can be used to coat the surface of avariety of implantable devices, for example: drug-delivering vascularstents; other vascular devices (e.g., grafts, catheters, valves,artificial hearts, heart assist devices); implantable defibrillators;blood oxygenator devices; surgical devices; tissue-related materials;membranes; cell culture devices; chromatographic support materials;biosensors; shunts for hydrocephalus; wound management devices;endoscopic devices; infection control devices; orthopedic devices;dental devices, urological devices; colostomy bag attachment devices;ophthalmic devices; glaucoma drain shunts; synthetic prostheses;intraocular lenses; respiratory, peripheral cardiovascular, spinal,neurological, dental, ear/nose/throat (e.g., ear drainage tubes); renaldevices; and dialysis (e.g., tubing, membranes, grafts).

Examples of useful devices include self-expanding stents (e.g., madefrom nitinol), balloon-expanded stents (e.g., prepared from stainlesssteel), degradable coronary stents, non-degradable coronary stents,peripheral coronary stents, urinary catheters (e.g., surface-coated withantimicrobial agents), penile implants, sphincter devices, urethraldevices, bladder devices, renal devices, vascular implants and grafts,intravenous catheters (e.g., treated with antithrombotic agents), smalldiameter grafts, artificial lung catheters, electrophysiology catheters,anastomosis devices, vertebral disks, bone pins, suture anchors,hemostatic barriers, clamps, surgicalstaples/sutures/screws/plates/clips, atrial septal defect closures,electro-stimulation leads for cardiac rhythm management (e.g., pacerleads), glucose sensors (long-term and short-term), blood pressure andstent graft catheters, blood oxygenator tubing, blood oxygenatormembranes, blood bags, birth control devices, breast implants, ); benignprostatic hyperplasia and prostate cancer implants, bonerepair/augmentation devices, breast implants, cartilage repair devices,orthopedic joint implants, orthopedic fracture repairs, tissueadhesives, tissue sealants, tissue scaffolds, CSF shunts, dentalimplants, dental fracture repair devices, implanted drug infusion tubes,intravitreal drug delivery devices, nerve regeneration conduits,oncological implants, electrostimulation leads, pain managementimplants, spinal/orthopedic repair devices, wound dressings, embolicprotection filters, abdominal aortic aneurysm grafts, heart valves(e.g., mechanical, polymeric, tissue, percutaneous, carbon, sewingcuff), valve annuloplasty devices, mitral valve repair devices, vascularintervention devices, left ventricle assist devices, neuro aneurysmtreatment coils, neurological catheters, left atrial appendage filters,central venous access catheters, hemodialysis devices, catheter cuff,anastomotic closures, vascular access catheters, cardiac sensors,uterine bleeding patches, urological catheters/stents/implants, in vitrodiagnostics, aneurysm exclusion devices, neuropatches, Vena cavafilters, urinary dialators, endoscopic surgical tissue extractors,atherectomy catheters, clot extraction catheters, PTA catheters, PTCAcatheters, stylets (vascular and non-vascular), coronary guidewires,drug infusion catheters, esophageal stents, circulatory support systems,angiographic catheters, transition sheaths and dialators, coronary andperipheral guidewires, hemodialysis catheters, neurovascular ballooncatheters, tympanostomy vent tubes, cerebro-spinal fluid shunts,defibrillator leads, percutaneous closure devices, drainage tubes,thoracic cavity suction drainage catheters, electrophysiology catheters,stroke therapy catheters, abscess drainage catheters, biliary drainageproducts, dialysis catheters, central venous access catheters, andparental feeding catheters.

The methods and compositions described herein are particularly usefulfor those devices that will come in contact with aqueous systems, suchas bodily fluids. Such devices can be coated with a coating compositionadapted to release bioactive agent in a prolonged and controlled manner,generally beginning with the initial contact between the device surfaceand its aqueous environment. It is important to note that the localdelivery of combinations of bioactive agents may be utilized to treat awide variety of conditions utilizing any number of medical devices, orto enhance the function and/or life of the device. Essentially, any typeof medical device may be coated in some fashion with one or morebioactive agents that enhances treatment over use of the singular use ofthe device or bioactive agent.

According to the invention, the biocompatible agent is utilized toprovide a biocompatible surface to a medical device. The solid surfacethat is rendered biocompatible is desirably of a synthetic or naturalmaterial that is insoluble, at least initially, in physiological fluids.The surface can be one or more surfaces of devices intended to functionin contact with tissue and/or fluids of living organisms.

According to the invention, the coating composition includes a polymericmaterial disposed or provided on the surface of a medical article. Thepolymers can be bio-stable or biodegradable, organic or inorganic, andsynthetic or naturally occurring substances. The polymeric material canbe selected from a variety of polymeric materials. Preferably, thepolymeric material has adherent properties, meaning that it can bedeposited on and stick to a surface.

In some aspects, the coating composition can be disposed on the medicalarticle having a surface that has been primed to facilitate adherence ofthe coating composition onto the medical article.

As used herein, “polymeric material” refers to homopolymers, copolymers,and combinations and mixtures thereof.

According to the invention, the polymeric material can be used in thebiocompatible coating composition or coated layer that includes thebiocompatible agent, in a bioactive active agent-containing layer orcomposition used to form this layer, or in another coated layer orcomposition, or combinations thereof.

In some embodiments, the coating composition includes a polymericmaterial that is selected to incorporate a desirable amount of thebioactive agent, and to either retain the bioactive agent so that it issufficiently presented to the surrounding physiological environment, orto release the bioactive agent to provide a desired elution profile.

Any suitable bio-stable or biodegradable polymeric materials can beused.

Bio-stable polymeric materials include, but are not limited to, polymersof polyurethanes, polyethylenes, polyethylene teraphthalates, ethylenevinyl acetates, silicones and polyethylene oxide. Ethylene vinyl alcoholcopolymers can also be used. Some preferred polymeric materials includemixtures of poly(butylmethacrylate) and poly(ethylene-co-vinyl acetate),and Parylene™. Bio-stable polymers can be permeable to the bioactiveagent, which can be released by diffusion through and out of thepolymeric material.

In some aspects, the invention provides a biocompatible, bioactiveagent-releasing coating that includes at least two layers, a bioactiveagent-releasing layer and a biocompatible layer. Both of these layerscan include a hydrophobic polymer. In some preferred aspects of theinvention, these layers include the same hydrophobic polymer. Thehydrophobic polymer is preferably a poly(alkyl(meth)acrylate), where“(meth)” will be understood by those skilled in the art to include suchmolecules in either the acrylic and/or methacrylic form (correspondingto the acrylates and/or methacrylates, respectively).

In one embodiment, the polymeric material comprises a composition asdescribed in U.S. Pat. No. 6,214,901 (Chudzik et al.) and US PublicationNo. 2002/0188037 Al (Chudzik et al.) (each commonly assigned to theassignee of the present invention). As described therein, thecomposition comprises a plurality of polymers, including at least twopolymer components, for example, primary and secondary polymercomponents. As used herein “primary” and “secondary” are used solely fordesignation of the polymer components are not intended to reflect therelative amounts of polymer components in the composition. The polymercomponents are adapted to be mixed to provide a mixture that exhibits anoptimal combination of physical characteristics (such as adherence,durability, flexibility) and bioactive release characteristics ascompared to the polymers when used alone or in admixture with otherpolymers previously known. For example the polymeric material caninclude an adherent polymer and a polymer having drug releasecharacteristics.

In some aspects the adherent polymer preferably includespoly(alkyl(meth)acrylates) and poly(aromatic (meth)acrylates), where“(meth)” will be understood by those skilled in the art to include suchmolecules in either the acrylic and/or methacrylic form (correspondingto the acrylates and/or methacrylates, respectively).

Examples of suitable poly(alkyl (meth)acrylates) include those withalkyl chain lengths from 2 to 8 carbons, inclusive, and with molecularweights from 50 kilodaltons to 900 kilodaltons. In one preferredembodiment the polymeric material includes a poly(alkyl (meth)acrylate)with a molecular weight of from about 100 kilodaltons to about 1000kilodaltons, preferably from about 150 kilodaltons to about 500kilodaltons, most preferably from about 200 kilodaltons to about 400kilodaltons. An example of a particularly preferred polymer is poly(n-butyl methacrylate). Examples of other preferred polymers arepoly(n-butyl methacrylate-co-methyl methacrylate, with a monomer ratioof 3:1, poly(n-butyl methacrylate-co-isobutyl methacrylate, with amonomer ratio of 1:1 and poly(t-butyl methacrylate). Such polymers areavailable commercially (e.g., from Sigma-Aldrich, Milwaukee, Wis.) withmolecular weights ranging from about 150 kilodaltons to about 350kilodaltons, and with varying inherent viscosities, solubilities andforms (e.g., as slabs, granules, beads, crystals or powder).

Examples of suitable poly(aromatic (meth)acrylates) include poly(aryl(meth)acrylates), poly(aralkyl (meth)acrylates), poly(alkaryl(meth)acrylates), poly(aryloxyalkyl (meth)acrylates), and poly(alkoxyaryl (meth)acrylates).

Examples of suitable poly(aryl (meth)acrylates) includepoly(9-anthracenyl methacrylate), poly(chlorophenyl acrylate),poly(methacryloxy-2-hydroxybenzophenone),poly(methacryloxybenzotriazole), poly(naphthyl acrylate),poly(naphthylmethacrylate), poly-4-nitrophenylacrylate,poly(pentachloro(bromo, fluoro) acrylate) and methacrylate, poly(phenylacrylate) and poly(phenyl methacrylate). Examples of suitablepoly(aralkyl (meth)acrylates) include poly(benzyl acrylate), poly(benzylmethacrylate), poly(2-phenethyl acrylate), poly(2-phenethylmethacrylate) and poly(1-pyrenylmethyl methacrylate). Examples ofsuitable poly(alkaryl(meth)acrylates include poly(4-sec-butylphenylmethacrylate), poly(3-ethylphenyl acrylate), andpoly(2-methyl-1-naphthyl methacrylate). Examples of suitablepoly(aryloxyalkyl (meth)acrylates) include poly(phenoxyethyl acrylate),poly(phenoxyethyl methacrylate), and poly(polyethylene glycol phenylether acrylate) and poly(polyethylene glycol phenyl ether methacrylate)with varying polyethylene glycol molecular weights. Examples of suitablepoly(alkoxyaryl(meth)acrylates) include poly(4-methoxyphenylmethacrylate), poly(2-ethoxyphenyl acrylate) and poly(2-methoxynaphthylacrylate).

Acrylate or methacrylate monomers or polymers and/or their parentalcohols are commercially available from Sigma-Aldrich (Milwaukee, Wis.)or from Polysciences, Inc, (Warrington, Pa.).

One of the other polymer components in the mixture provides an optimalcombination of similar properties, and particularly when used inadmixture with the primary polymer component. Examples of suitablesecondary polymers are available commercially and includepoly(ethylene-co-vinyl acetate) having vinyl acetate concentrations inthe range of about 1% to about 50%, in the form of beads, pellets,granules, and the like.

In some embodiments, the composition comprises at least onepoly(alkyl)(meth)acrylate, as a primary, adherent polymeric component,and poly(ethylene-co-vinyl acetate) as a secondary polymeric component.Preferably, the polymer mixture includes mixtures ofpoly(butylmethacrylate) (PBMA) and poly(ethylene-co-vinyl acetate)(pEVA). This mixture of polymers has proven useful with absolute polymerconcentrations (total combined concentrations of both polymers in thecomposition) in the range of about 0.25 to about 70% (by weight). It hasfurthermore proven effective with individual polymer concentrations inthe coating solution in the range of about 0.05 to about 70% (byweight). In one preferred embodiment, the polymer mixture includes poly(n-butylmethacrylate) (PBMA) with a molecular weight in the range ofabout 100 kD to 900 kD and a pEVA copolymer with a vinyl acetate contentin the range of about 24 to 36% (by weight). In another preferredembodiment, the polymer mixture includes poly (n-butylmethacrylate)(PBMA) with a molecular weight in the range of about 200 kD to 400 kDand a pEVA copolymer with a vinyl acetate content in the range of about30 to 34% (by weight). According to these embodiments, the concentrationof the bioactive agent or agents dissolved or suspended in the coatingmixture can be in the range of about 0.01 to 90%, by weight, based onthe weight of the final coating composition.

Other useful mixtures of polymers that can be included in the coatingcomposition are described in commonly assigned U.S. Patent Applicationentitled, “COATING COMPOSITIONS FOR BIOACTIVE AGENTS,” having attorneydocket number 9896.166.1. These blends includes a first polymer and asecond polymer. The first polymer can be selected from the groupconsisting of (i) poly(alkylene-co-alkyl(meth)acrylates, (ii) ethylenecopolymers with other alkylenes, (iii) polybutenes, (iv) diolefinderived non-aromatic polymers and copolymers, (v) aromaticgroup-containing copolymers, and (vi) epichlorohydrin-containingpolymers. A second polymer can be selected from the group consisting ofpoly(alkyl (meth)acrylates) and poly(aromatic(meth)acrylates).

Other useful mixtures of polymers that can be included in the coatingare described in U.S. Publication No. 2004/0047911. This publicationdescribes polymer blends that include poly(ethylene-co-methacrylate) anda polymer selected from the group consisting of a poly(vinyl alkylate),a poly(vinyl alkyl ether), a poly(vinyl acetal), a poly(alkyl and/oraryl methacrylate) or a poly(alkyl and/or aryl acrylate); not includingpEVA.

The polymeric material can also be a styrene copolymer, such aspoly(styrene-isobutylene-styrene); the preparation of medical deviceshaving such coatings that include poly(styrene-isobutylene-styrene) isdescribed in, for example, U.S. Pat. No. 6,669,980.

In some embodiments, the biocompatible, bioactive agent-releasingcoating includes a tie layer. The tie layer can improve association ofthe bioactive agent-releasing layer with the article itself, and caninclude any sort of material which is compatible with the function ofthe article. Particularly useful materials include polymeric material,such as Parylene™ or a Parylene™ derivative.

In some embodiments, the polymeric material comprises Parylene™ or aParylene™ derivative. “Parylene” is both a generic name for a knowngroup of polymers based on p-xylylene and made by vapor phasepolymerization, and a name for the unsubstituted form of the polymer;the latter usage is employed herein. More particularly, Parylene™ or aParylene™ derivative is created by first heating p-xylylene or asuitable derivative at an appropriate temperature (for example, at about100-1 50° C.) to produce the cyclic dimer di-p-xylylene (or a derivativethereof). The resultant solid can be separated in pure form, and thencracked and pyrolyzed at an appropriate temperature (for example, atabout 690° C.) to produce a monomer vapor of p-xylylene (or derivative);the monomer vapor is cooled to a suitable temperature (for example,below 30° C.) and allowed to condense on the desired object, forexample, on the surface of the medical device.

As indicated, Parylene™ and Parylene™ derivative coatings applicable byvapor deposition are known for a variety of biomedical uses, and arecommercially available from or through a variety of sources, includingSpecialty Coating Systems (100 Deposition Drive, Clear Lake, Wis.54005), Para Tech Coating, Inc. (35 Argonaut, Aliso Viejo, Calif. 92656)and Advanced Surface Technology, Inc. (9 Linnel Circle, Billerica, Mass.01821-3902).

As used herein, biodegradable polymers are capable of being broken downby various enzymes, such as those in the normal functioning of the humanbody and living organisms (such as bacteria) and/or in waterenvironments (simple hydrolysis). Once broken down, these polymers aregradually absorbed or eliminated by the body.

Examples of classes of synthetic polymers that have been studied asbiodegradable materials include polyesters, polyamides, polyurethanes,polyorthoesters, polycaprolactone (PCL), polyiminocarbonates, aliphaticcarbonates, polyphosphazenes, polyanhydrides, and copolymers thereof.Specific examples of biodegradable materials that can be used inconnection with implantable medical devices include polylactide,polygylcolide, polydioxanone, poly(lactide-co-glycolide),poly(glycolide-co-polydioxanone), polyanhydrides,poly(glycolide-co-trimethylene carbonate), andpoly(glycolide-co-caprolactone). Blends of these polymers with otherbiodegradable polymers can also be used. Typically, release of abioactive agent occurs as these polymers dissolve or degrade in situ.

Biodegradable polyetherester copolymers can be used. Generally speaking,the polyetherester copolymers are amphiphilic block copolymers thatinclude hydrophilic (for example, a polyalkylene glycol, such aspolyethylene glycol) and hydrophobic blocks (for example, polyethyleneterephthalate). Examples of block copolymers include poly(ethyleneglycol)-based and poly(butylene terephthalate)-based blocks (PEG/PBTpolymer). Examples of these types of multiblock copolymers are describedin, for example, U.S. Pat. No. 5,980,948. PEG/PBT polymers arecommercially available from Octoplus BV, under the trade designationPolyActive™.

Biodegradable copolymers having a biodegradable, segmented moleculararchitecture that includes at least two different ester linkages canalso be used. The biodegradable polymers can be block copolymers (of theAB or ABA type) or segmented (also known as multiblock or random-block)copolymers of the (AB)_(n) type. These copolymers are formed in a two(or more) stage ring opening copolymerization using two (or more) cyclicester monomers that form linkages in the copolymer with greatlydifferent susceptibilities to transesterification. Examples of thesepolymers are described in, for example, in U.S. Pat. No. 5,252,701(Jarrett et al., “Segmented Absorbable Copolymer”).

Other suitable biodegradable polymer materials include biodegradableterephthalate copolymers that include a phosphorus-containing linkage.Polymers having phosphoester linkages, called poly(phosphates),poly(phosphonates) and poly(phosphites), are known. See, for example,Penczek et al., Handbook of Polymer Synthesis, Chapter 17:“Phosphorus-Containing Polymers,” 1077-1132 (Hans R. Kricheldorf ed.,1992), as well as U.S. Pat. Nos. 6,153,212, 6,485,737, 6,322,797,6,600,010, 6,419,709. Biodegradable terephthalate polyesters can also beused that include a phosphoester linkage that is a phosphite. Suitableterephthalate polyester-polyphosphite copolymers are described, forexample, in U.S. Pat. No. 6,419,709 (Mao et al., “BiodegradableTerephthalate Polyester-Poly(Phosphite) Compositions, Articles, andMethods of Using the Same). Biodegradable terephthalate polyester canalso be used that include a phosphoester linkage that is a phosphonate.Suitable terephthalate polyester-poly(phosphonate) copolymers aredescribed, for example, in U.S. Pat. Nos. 6,485,737 and 6,153,212 (Maoet al., “Biodegradable Terephthalate Polyester-Poly(Phosphonate)Compositions, Articles and Methods of Using the Same). Biodegradableterephthalate polyesters can be used that include a phosphoester linkagethat is a phosphate. Suitable terephthalate polyester-poly(phosphate)copolymers are described, for example, in U.S. Pat. Nos. 6,322,797 and6,600,010 (Mao et al., “Biodegradable TerephthalatePolyester-Poly(Phosphate) Polymers, Compositions, Articles, and Methodsfor Making and Using the Same).

Biodegradable polyhydric alcohol esters can also be used (See U.S. Pat.No. 6,592,895). This patent describes biodegradable star-shaped polymersthat are made by esterifying polyhydric alcohols to provide acylmoieties originating from aliphatic homopolymer or copolymer polyesters.The biodegradable polymer can be a three-dimensional crosslinked polymernetwork containing hydrophobic and hydrophilic components which forms ahydrogel with a crosslinked polymer structure, such as that described inU.S. Pat. No. 6,583,219. The hydrophobic component is a hydrophobicmacromer with unsaturated group terminated ends, and the hydrophilicpolymer is a polysaccharide containing hydroxy groups that are reactedwith unsaturated group introducing compounds. The components areconvertible into a one-phase crosslinked polymer network structure byfree radical polymerization. In yet further embodiments, thebiodegradable polymer can comprise a polymer based upon α-amino acids(such as elastomeric copolyester amides or copolyester urethanes, asdescribed in U.S. Pat. No. 6,503,538).

In some aspects, the polymeric material is a hydrophobic polymer thatcan provide certain properties to the biocompatible layer, includingpliability and drug-releasing properties. In some aspects of theinvention, the hydrophobic polymer is present in the biocompatible layerin an amount sufficient to provide good pliability to the coating. Anysuitable hydrophobic polymers can be used, and in many cases, can bechosen from those described herein.

In some preferred aspects, the amount of hydrophobic polymer is presentin the biocompatible coated layer in the range of about 40% to about 90%(as based on total weight of the coated layer, and more preferably inthe range of about 75% to about 90%.

In some embodiments, the bioactive agent-releasing layer can include oneor more bioactive agents. In preferred aspects, the bioactive agent isreleased by particle dissolution or diffusion. It is understood that therelease of the bioactive agent will generally include the bioactiveagent passing through the biocompatible layer before being releaselocally into the adjacent or surrounding tissue.

In some embodiments, the coating includes a bioactive agent-releasinglayer which includes a bioactive agent that can be prepared incombination with the polymeric materials of the bioactive agent coatingcomposition. Preferably the bioactive agent can be released from thecoating, including the biocompatible portion of the coating, in acontrolled manner. Exemplary and preferred bioactive agents include, butare not limited to, antibiotics, anti-inflammatory agents,anti-proliferative agents, immunomodulatory agents, and anti-mitotics.Particularly useful bioactive agents of these classes include macrolideantibiotics such as rapamycin (triene macrolide antibiotic) andrapamycin analogs; immunomodulatory agents such as ABT-578; andanti-mitotics including taxoid drugs such as paclitaxel and docetaxel.Other useful bioactive agents are discussed herein.

In other embodiments, the coating composition can include one or morebioactive agents, or one or more bioactive agents can be added to thecoating composition. The bioactive agent can be released by particledissolution or diffusion when bio-stable matrices are used, or duringpolymer breakdown when absorbed into a biodegradable substance.Alternatively, one or more bioactive agents can be presented to thephysiological environment without being released from the polymericmaterial. For example, the bioactive agent(s) can be covalently coupledto the polymeric material so that the agent(s) are not released from thepolymeric material into the physiological environment.

The coating composition on the medical device can comprise one or morebioactive agents incorporated into a polymeric material so that thebioactive agent is presented to or released locally into the adjacent orsurrounding tissue. If released, the bioactive agent is preferablyreleased in a slow or controlled-release manner, to provide the desiredelution profile to achieve the therapeutic effect. The release of thebioactive agent in a controlled release manner allows for smalleramounts of the bioactive agent to be released for a long period of timein a zero order elution profile manner. The release kinetics of thebioactive agent can further depend upon such factors as thehydrophobicity of the bioactive agent (for example, a more hydrophobicbioactive agent typically exhibits a slower the rate of release from thepolymeric material). Alternatively, hydrophilic bioactive agents can bereleased from the polymeric material at a faster rate. Therefore, thepolymeric composition can be altered according to the bioactive agent tobe delivered in order to maintain the desired concentration of bioactiveagent required at the treatment site for a longer period of time. Aswill be apparent upon review of this disclosure, the medical device cantherefore provide a long-term effect of the bioactive agent at thetreatment site that is more efficient in preventing restenosis andreduces side effects of the bioactive agents utilized.

An improvement in the function of a bioactive agent-releasing coatingmay be seen when the biocompatible layer minimizes the accumulation ofblood components that may otherwise get deposited on the bioactive agentreleasing layer. By reducing these factors, this may improve thefunction of the bioactive agent releasing layer.

For purposes of the description herein, reference will be made to“bioactive agent,” but it is understood that the use of the singularterm does not limit the application of bioactive agents contemplated,and any number of bioactive agents can be provided using the teachingherein. As used herein, “bioactive agent” refers to an agent thataffects physiology of biological tissue. Bioactive agents usefulaccording to the invention include virtually any substance thatpossesses desirable therapeutic characteristics for application to theimplantation site.

It is important to note that the local delivery of combinations ofbioactive agents may be utilized to treat a wide variety of conditionsutilizing any number of medical devices, or to enhance the functionand/or life of the device. Essentially, any type of medical device maybe coated in some fashion with one or more bioactive agents thatenhances treatment over use of the singular use of the device orbioactive agent.

The word “bioactive agent,” as used herein, will refer to a wide rangeof biologically active materials or drugs that can be incorporated intoa coating composition of the present invention. The bioactive agent(s)to be incorporated preferably do not chemically interact with thecoating composition during fabrication or during the bioactive agentrelease process.

The term “bioactive agent,” in turn, will refer to a synthetic inorganicor organic molecule that causes a biological effect when administered invivo to an animal, including but not limited to birds and mammals,including humans. Nonlimiting examples are antigens, enzymes, hormones,receptors, peptides, and gene therapy agents. Examples of suitable genetherapy agents include a) therapeutic nucleic acids, including antisenseDNA and antisense RNA, and b) nucleic acids encoding therapeutic geneproducts, including plasmid DNA and viral fragments, along withassociated promoters and excipients. Examples of other molecules thatcan be incorporated include nucleosides, nucleotides, antisense,vitamins, minerals, and steroids.

Coating compositions prepared according to this process can be used todeliver drugs such as nonsteroidal anti-inflammatory compounds,anesthetics, chemotherapeutic agents, immunotoxins, immunosuppressiveagents, steroids, antibiotics, antivirals, antifungals, steroidalantiinflammatories, and anticoagulants. For example, hydrophobic drugssuch as lidocaine or tetracaine can be included in the coating and arereleased over several hours.

Classes of medicaments which can be incorporated into coatings of thisinvention include, but are not limited to, anti-AIDS substances,anti-cancer substances, antibiotics, anti-viral substances, enzymeinhibitors, neurotoxins, opioids, hypnotics, antihistamines,immunosuppressants (e.g., cyclosporine), tranquilizers,anti-convulsants, muscle relaxants and anti-Parkinson substances,anti-spasmodics and muscle contractants, miotics and anti-cholinergics,immunosuppressants (e.g. cyclosporine), anti-glaucoma solutes,anti-parasite and/or anti-protozoal solutes, anti-hypertensives,analgesics, anti-pyretics and anti-inflammatory agents (such as NSAIDs),local anesthetics, ophthalmics, prostaglandins, anti-depressants,anti-psychotic substances, anti-emetics, imaging agents, specifictargeting agents, neurotransmitters, proteins, and cell responsemodifiers. A more complete listing of classes of medicaments may befound in the Pharmazeutische Wirkstoffe, ed. A. Von Kleemann and J.Engel, Georg Thieme Verlag, Stuttgart/N.Y., 1987, incorporated herein byreference.

Antibiotics are art recognized and are substances which inhibit thegrowth of or kill microorganisms. Antibiotics can be producedsynthetically or by microorganisms. Examples of antibiotics includepenicillin, tetracycline, chloramphenicol, minocycline, doxycycline,vancomycin, bacitracin, kanamycin, neomycin, gentamycin, erythromycin,cephalosporins, geldanamycin, and analogs thereof. Examples ofcephalosporins include cephalothin, cephapirin, cefazolin, cephalexin,cephradine, cefadroxil, cefamandole, cefoxitin, cefaclor, cefuroxime,cefonicid, ceforanide, cefotaxime, moxalactam, ceftizoxime, ceftriaxone,and cefoperazone.

Antiseptics are recognized as substances that prevent or arrest thegrowth or action of microorganisms, generally in a nonspecific fashion,e.g., either by inhibiting their activity or destroying them. Examplesof antiseptics include silver sulfadiazine, chlorhexidine,glutaraldehyde, peracetic acid, sodium hypochlorite, phenols, phenoliccompounds, iodophor compounds, quaternary ammonium compounds, andchlorine compounds.

Anti-viral agents are substances capable of destroying or suppressingthe replication of viruses. Examples of anti-viral agents includeα-methyl-P-adamantane methylamine, hydroxyethoxymethylguanine,adamantanamine, 5-iodo-2′-deoxyuridine, trifluorothymidine, interferon,and adenine arabinoside.

Enzyme inhibitors are substances that inhibit an enzymatic reaction.Examples of enzyme inhibitors include edrophonium chloride,N-methylphysostigmine, neostigmine bromide, physostigmine sulfate,tacrine.HCl, tacrine, 1-hydroxymaleate, iodotubercidin,p-bromotetramisole, 10-(α-diethylaminopropionyl)-phenothiazinehydrochloride, calmidazolium chloride,hemicholinium-3,3,5-dinitrocatechol, diacylglycerol kinase inhibitor I,diacylglycerol kinase inhibitor II, 3-phenylpropargylaminie,N-monomethyl-L-arginine acetate, carbidopa, 3-hydroxybenzylhydrazineHCl, hydralazine HCl, clorgyline HCl, deprenyl HCl, L(−), deprenyl HCl,D(+), hydroxylamine HCl, iproniazid phosphate,6-MeO-tetrahydro-9H-pyrido-indole, nialamide, pargyline HCl, quinacrineHCl, semicarbazide HCl, tranylcypromine HCl,N,N-diethylaminoethyl-2,2-diphenylvalerate hydrochloride,3-isobutyl-1-methylxanthne, papaverine HCl, indomethacin,2-cyclooctyl-2-hydroxyethylamine hydrochloride,2,3-dichloro-a-methylbenzylamine(DCMB),8,9-dichloro-2,3,4,5-tetrahydro-1H-2-benzazepine hydrochloride,p-aminoglutethimide, p-aminoglutethimide tartrate, R(+),p-aminoglutethimide tartrate, S(−), 3-iodotyrosine,alpha-methyltyrosine, L(−), alpha-methyltyrosine, D L(−), cetazolamide,dichlorphenamide, 6-hydroxy-2-benzothiazolesulfonamide, and allopurinol.

Anti-pyretics are substances capable of relieving or reducing fever.Anti-inflammatory agents are substances capable of counteracting orsuppressing inflammation. Examples of such agents include aspirin(salicylic acid), indomethacin, sodium indomethacin trihydrate,salicylamide, naproxen, colchicine, fenoprofen, sulindac, diflunisal,diclofenac, indoprofen and sodium salicylamide. Local anesthetics aresubstances which have an anesthetic effect in a localized region.Examples of such anesthetics include procaine, lidocaine, tetracaine anddibucaine.

Imaging agents are agents capable of imaging a desired site, e.g.,tumor, in vivo. Examples of imaging agents include substances having alabel which is detectable in vivo, e.g., antibodies attached tofluorescent labels. The term antibody includes whole antibodies orfragments thereof.

Cell response modifiers are chemotactic factors such as platelet-derivedgrowth factor (pDGF). Other chemotactic factors includeneutrophil-activating protein, monocyte chemoattractant protein,macrophage-inflammatory protein, SIS (small inducible secreted),platelet factor, platelet basic protein, melanoma growth stimulatingactivity, epidermal growth factor, transforming growth factor (alpha),fibroblast growth factor, platelet-derived endothelial cell growthfactor, insulin-like growth factor, nerve growth factor, and bonegrowth/cartilage-inducing factor (alpha and beta). Other cell responsemodifiers are the interleukins, interleukin inhibitors or interleukinreceptors, including interleukin 1 through interleukin 10; interferons,including alpha, beta and gamma; hematopoietic factors, includingerythropoietin, granulocyte colony stimulating factor, macrophage colonystimulating factor and granulocyte-macrophage colony stimulating factor;tumor necrosis factors, including alpha and beta; transforming growthfactors (beta), including beta-1, beta-2, beta-3, inhibin, activin, andDNA that encodes for the production of any of these proteins.

Additives such as inorganic salts, BSA (bovine serum albumin), and inertorganic compounds can be used to alter the profile of bioactive agentrelease, as known to those skilled in the art.

The bioactive (e.g., pharmaceutical) agents useful in the presentinvention include virtually any therapeutic substance that possessesdesirable therapeutic characteristics for application to the implantsite. These agents include: thrombin inhibitors, antithrombogenicagents, thrombolytic agents, fibrinolytic agents, vasospasm inhibitors,calcium channel blockers, vasodilators, antihypertensive agents,antimicrobial agents, antibiotics, inhibitors of surface glycoproteinreceptors, antiplatelet agents, antimitotics, microtubule inhibitors,anti secretory agents, actin inhibitors, remodeling inhibitors,antisense nucleotides, anti metabolites, antiproliferatives (includingantiangiogenesis agents), anticancer chemotherapeutic agents,anti-inflammatory steroid or non-steroidal anti-inflammatory agents,immunosuppressive agents, growth hormone antagonists, growth factors,dopamine agonists, radiotherapeutic agents, peptides, proteins, enzymes,extracellular matrix components, ACE inhibitors, free radicalscavengers, chelators, antioxidants, anti polymerases, antiviral agents,photodynamic therapy agents, gene therapy agents, and statins (such aslovastatin, pravastatin, simvastatin, fluvastatin, atorvastatin,cerivastatin, rousvastatin, and superstatin)

Other examples of suitable bioactive agents include sirolimus(rapaamycin), analogues of rapamycin (“rapalogs”), tacrolimus, ABT-578from Abbott, everolimus, paclitaxel, taxane, dexamethasone,betamethasone, paclitaxel, vinblastine, vincristine, vinorelbine,poside, teniposide, dactinomycin (actinomycin D), daunorubicin,doxorubicin, idarubicin, anthracyclines, mitoxantrone, bleomycins,plicamycin (mithramycin), mitomycin, mechlorethamine, cyclophosphamideand its analogs, melphalan, chlorambucil, ethylenimines andmethylmelamines, alkyl sulfonates-busulfan, nirtosoureas, carmustine(BCNU) and analogs, streptozocin, trazenes-dacarbazinine, methotrexate,fluorouracil, floxuridine, cytarabine, mercaptopurine, thioguanine,pentostatin, 2-chlorodeoxyadenosine, cisplatin, carboplatin,procarbazine, hydroxyurea, mitotane, aminoglutethimide, estrogen,heparin, synthetic heparin salts, tissue plasminogen activator,streptokinase, urokinase, aspirin, dipyridamole, ticlopidine,clopidogrel, abciximab, breveldin, cortisol, cortisone, fludrocortisone,prednisone, prednisolone, 6U-methylprednisolone, triamcinolone, aspirin,acetaminophen, indomethacin, sulindac, etodalac, tolmetin, diclofenac,ketorolac, ibuprofen and derivatives, mefenamic acid, meclofenamic acid,piroxicam, tenoxicam, phenylbutazone, oxyphenthatrazone, nabumetone,auranofin, aurothioglucose, gold sodium thiomalate, cyclosporine,tacrolimus (FK-506), azathioprine, mycophenolate mofetil, vascularendothelial growth factor (VEGF), fibroblast growth factor (FGF);angiotensin receptor blocker; nitric oxide donors; anti-senseoligionucleotides and combinations thereof; cell cycle inhibitors, mTORinhibitors, and growth factor signal transduction kinase inhibitors.

A comprehensive listing of bioactive agents can be found in The MerckIndex, Thirteenth Edition, Merck & Co. (2001). Bioactive agents arecommercially available from Sigma Aldrich Fine Chemicals, Milwaukee,Wis.

The concentration of the bioactive agent or agents dissolved orsuspended in the coating mixture can range from about 0.01 to about 90percent, by weight, based on the weight of the final coated composition.

The particular bioactive agent, or combination of bioactive agents, canbe selected depending upon one or more of the following factors: theapplication of the controlled delivery device, the medical condition tobe treated, the anticipated duration of treatment, characteristics ofthe implantation site, the number and type of bioactive agents to beutilized, and the like.

In some aspects, the coating includes a bioactive agent-releasing layerwhich can be adjacent to one or more other coated layers which canoptionally be present in the coating. (For purposes of discussion, andalso to describe various aspects of the invention, the coated layers mayalso be described by “first coated layer”, “second coated layer”, and,if necessary, so forth. However, the nomenclature that is used may beprimarily for the convenience of describing various aspects of theinvention. For example, when describing a coating with two layers,whether a “first layer” is distal or proximal to the surface of thedevice will be understood in the context of the specific description ofthat coating.)

If desired, optionally, the surface of the article can be treated toimprove the association of components present in a subsequent coatedlayer. For example, the surface of the article may be pretreated with asilane-containing component (in these aspects, for example, this may bereferred to as the first coated layer). In some cases, the coating canoptionally include a base or “tie layer” that is between the surface ofthe article and the bioactive agent-releasing layer. The tie layer,which is optional, but present in some preferred embodiments, canimprove the association of components that are subsequently coated onthe article, such as components present in the bioactive-agent releasinglayer. The tie layer can include a material, such as Parylene™ that isadhered or bonded to the surface of the article.

Optionally, in some embodiments of the invention, an intermediate coatedlayer can be present between the bioactive agent-releasing layer and thebiocompatible layer. In some aspects, for example, when the bioactiveagent-releasing layer is immediately adjacent to the (uncoated) surfaceof the article, this intermediate layer can be a “second coated layer”,or one or more layers is present between the bioactive agent-releasingcoating and the surface, this intermediate layer can be the third,fourth, etc., coated layer. This intermediate layer can include one ormore compounds that are present in either, or both, of the bioactiveagent-releasing layer and/or biocompatible layer. In some aspects, thiscoated layer can include a polymeric component present in the bioactiveagent-releasing layer. For example, this intermediate layer can includepoly(alkyl(meth)acrylates) having a short chain alkyl group, such asthose in the range of C₂-C₅, including propyl (C₃), and most preferablybutyl (C₄). Most preferably this intermediate layer includes preferablya poly(alkyl(meth)acrylate), such as pBMA.

Other coated layers may also be present between the bioactiveagent-releasing layer and the biocompatible layer. Although these layersare optional, they may be formed to change or improve aspects of thecoating.

In other embodiments of the invention, a bioactive agent can be addedto, or is present in the coating composition. For example, in someaspects, a composition containing the polymeric material, abiocompatible agent, and a photoreactive moiety is prepared. Thecomposition is then treated to couple the biocompatible agent to thepolymeric material via the photoreactive group. After this treatment abioactive agent is added to the composition. The composition containingthe bioactive agent is then disposed on a substrate. Alternatively, thecoating composition is first disposed on the substrate and then thebioactive agent is added to the coating.

The invention generally provides methods for preparing a biocompatiblesurface on a medical article. According to the invention, biocompatibleagents can be selected to improve the compatibility (for example, withblood and surrounding tissues) of medical device surfaces. In preferredembodiments, the biocompatible agent, when coupled to the medical devicesurface, can serve to shield the blood from the underlying medicaldevice material. Suitable biocompatible agents preferably reduce thelikelihood for blood components to adhere to the medical device andactivate, thus reducing the formation of thrombus or emboli (blood clotsthat release and travel downstream.

The biocompatible agent can be essentially any biomolecule that isattached to the solid surfaces of medical articles to improvebiocompatibility of the medical article. Thus, the description ofbioactive agents suitable for use in the polymeric material isinstructive for selection of the biocompatible agents as well.

In some aspects, the biocompatible agent is a biocompatible polymer.According to the invention, biocompatible polymers can be selected toimprove the compatibility (for example, with blood and surroundingtissues) of medical device surfaces. In preferred embodiments, thebiocompatible polymer, when coupled to the medical device surface, canserve to shield the blood from the underlying medical device material.Suitable biocompatible polymers preferably reduce the likelihood forblood components to adhere to the medical device and activate, thusreducing the formation of thrombus or emboli (blood clots that releaseand travel downstream.

The biocompatible polymer can be essentially any polymer that canimprove biocompatibility of the medical article.

Representative examples of biocompatible polymers (including peptidesand proteins) having antithrombotic effects include heparin, heparinderivatives, sodium heparin, low molecular weight heparin, hirudin,polylysine, argatroban, glycoprotein IIb/IIIa platelet membrane receptorantibody, coprotein IIb/IIIa platelet membrane receptor antibody,recombinant hirudin, thrombin inhibitor (such as commercially availablefrom Biogen), chondroitin sulfate, modified dextran, albumin,streptokinase, and tissue plasminogen activator (TPA).

Other contemplated biocompatible polymers include fibronectin, laminin,collagen, elastin, vitronectin, tenascin, fibrinogen, thrombospondin,osteopontin, von Willibrand Factor, bone sialoprotein and active domainsthereof), or a hydrophilic polymer such as hyaluronic acid, chitosan ormethyl cellulose.

Exemplary cell-cell adhesion molecules include N-cadherin and P-cadherinand active domains thereof.

Exemplary growth factors include fibroblastic growth factors, epidermalgrowth factor, platelet-derived growth factors, transforming growthfactors, vascular endothelial growth factor, bone morphogenic proteinsand other bone growth factors, and neural growth factors.

Exemplary ligands or receptors include antibodies, antigens, avidin,streptavidin, and biotin.

In some aspects, the biocompatible polymer is present in the coating inan amount sufficient to provide a therapeutically useful amount ofbiocompatible activity to the surface of the device. For example, insome aspects, the coating provides heparin activity in an amount thateither prevents or reduces the accumulation of clotting factors over aperiod of time during which the device is used.

In some preferred aspects, the amount of hydrophilic biocompatiblepolymer (for example, heparin) is present in the biocompatible coatedlayer in the range of about 5% to about 25% (as based on total weight ofthe coated layer), and more preferably in the range of about 5% to about15%.

In preferred aspects, the hydrophilic biocompatible polymer has one ormore pendent photoreactive groups. The photoreactive group can bependent from the polymer in an amount that allows for the formation of astable coated layer that provides biocompatibility, such as heparinactivity. One exemplary hydrophilic biocompatible polymer with pendentphotoreactive groups is photo-heparin, which is described herein. Thehydrophilic biocompatible polymer with pendent photoreactive groups canbe used with other photoreactive components in the biocompatible coatingcomposition.

In some aspects, the method of providing a biocompatible coating to amedical device can also include a step of disposing a secondbiocompatible agent, which can be different or the same as thebiocompatible agent of the coating compound, on the medical article,such as to provide a second coating to the medical article. The secondbiocompatible agent can include reactive groups such as photoreactivegroups. The step of disposing a second biocompatible agent can provide atop coat to the medical article.

In a preferred aspect of the invention, a miscibility enhancer is addedto the biocompatible coating composition. A miscibility enhancer can beused to improve the homogeneity of the polymeric material and thebiocompatible agent in the coating composition and improve the overallcoating composition. According to the invention, the miscibilityenhancer can be used improve the coupling of the biocompatible agent tothe polymer, for example, an adherent polymer.

The miscibility enhancer can be selected from the group consisting ofpolyvinylpyrrolidinone (PVP), polyethyleneglycol (PEG), PEG sulfonates,fatty quaternary amines, fatty sulfonates, fatty acids, dextran,dextrin, and cyclodextrin. The miscibility enhancer can also includependant photoreactive groups.

Preferably, the miscibility enhancer is a polymeric material, in someaspects, is the third polymer of the biocompatible layer. A1-vinyl-2-pyrrolidone homopolymer or copolymer is preferred, hereinreferred to as a “poly(vinylpyrrolidone)” (PVP). PVP is a tertiary amidebased polymer. In some preferred aspects, the PVP component has amolecular weight of about 1×10⁶ Da or less.

In some preferred aspects, the amount of PVP is present in thebiocompatible coated layer in the range of about 5% to about 50% (asbased on total weight of the coated layer), and more preferably in therange of about 5% to about 15%.

If a PVP copolymer is used, it can be a copolymer of VP and a monomerselected from the group of hydrophilic monomers. Exemplary hydrophilicmonomers include (meth)acrylamide and (meth)acrylamide derivatives, suchas alkyl(meth)acrylamide and aminoalkyl(meth)acrylamide, such asaminopropylmethacrylamide and dimethylaminopropyl-methacrylamide. Use ofPVP copolymers is particularly advantageous for the preparation and useof PVP derivitized with photoreactive groups.

PVP copolymers can be prepared to change the properties of PVP, forexample, poly(vinylpyrrolidone-co-vinyl acetate) polymers can beprepared which can be more hydrophobic and gives less brittle films.Poly(vinylpyrrolidone) can be prepared by polymerization of1-vinyl-2-pyrrolidone in water using hydrogen peroxide as an initiator.Methods for terminating the polymerization VP can allow the preparationof PVP of numerous molecular weights.

The coated layer also includes photoreactive groups that have beenactivated and reacted to bond to one or more compound(s) present in thecoating. “Activated” means that the photoreactive groups have beentreated with an activating sources of radiation, thereby having excitedthe groups to an active state which resulted in the bonding the groupsto one or more other components in the coating composition. Use ofphotoreactive groups is particularly advantageous as used in the presentinvention for many reasons. For example, use of photoreactive groupsallows the timing of bond formation to be controlled with highprecision. For example, at one or more points during the coating processthe photogroups can be activated for a desired length of time. Use ofphotoreactive groups also allows one to control the extent of bondformation by controlling the amount of applied activating energy.Knowing the composition of the coating and other materials associatedwith the coated surface, the use of photogroups can allow bond formationbetween particular targets and not others. Also, a photoreactive groupcan be chosen to absorb activating energy at particular wavelengths andnot others. This can be beneficial if components, such as bioactiveagents, in the coating are sensitive to particular wavelengths of light.

The photoreactive moiety can be pendent from the biocompatible agent orpolymeric material. Alternatively, or additionally, the photoreactivemoiety is independent of the polymeric material or the biocompatibleagent in the coating composition.

In some embodiments the photoreactive moiety is independent of thepolymeric material and the biocompatible material and can be, forexample, a crosslinking agent. Exemplary crosslinking gents aredescribed in Applicant's U.S. Pat. No. 5,414,075 (Swan et al.), and U.S.Publication No. 2003/0165613 A1 (Chappa et al.). See also U.S. Pat. No.5,714,360 (Swan et al.) and U.S. Pat. No. 5,637,460 (Swan et al.).

In one such embodiment described in these references, the crosslinkingagent can comprise a chemical nonpolymeric core molecule having attachedto it one or more first latent reactive groups and one or more secondlatent reactive groups.

In some preferred embodiments, the crosslinking reagent is selected fromtetrakis (4-benzoylbenzyl ether), the tetrakis (4-benzoylbeonzoateester) of pentaerythritol, and an acylated derivative oftetraphenylmethane.

A “latent reactive group,” as used herein, refers to a chemical groupthat responds to an applied external energy source in order to undergoactive specie generation, resulting in covalent bonding to an adjacentchemical structure (via an abstractable hydrogen). Preferred groups aresufficiently stable to be stored under conditions in which they retainsuch properties. See, for example, U.S. Pat. No. 5,002,582 (Guire etal.). Latent reactive groups can be chosen that are responsive tovarious portions of the electromagnetic spectrum, with those responsiveto ultraviolet and visible portions of the spectrum (referred to hereinas “photoreactive”) being particularly preferred.

In preferred embodiments a photoreactive group is pendent from thebiocompatible agent. In other preferred embodiments a photoreactivegroup is pendent from the miscibility enhancer or pendent from both thebiocompatible agent and the miscibility enhancer.

Photoreactive species responds to a specific applied externalultraviolet or visible light source to undergo active specie generationwith resultant covalent bonding to an adjacent chemical structure, forexample, as provided by the same or a different molecule. Photoreactivespecies are those groups of atoms in a molecule that retain theircovalent bonds unchanged under conditions of storage but that, uponactivation by a specific applied external ultraviolet or visible lightsource form covalent bonds with other molecules.

Latent reactive (for example, photoreactive) species generate activespecies such as free radicals and particularly nitrenes, carbenes, andexcited states of ketones, upon absorption of electromagnetic energy.Latent reactive species can be chosen to be responsive to variousportions of the electromagnetic spectrum, and photoreactive species thatare responsive to the ultraviolet and visible portions of the spectrumare preferred and can be referred to herein as “photoreactive groups” or“photoreactive moieties.”

The latent reactive species in latent reactive aryl ketones arepreferred, such as acetophenone, benzophenone, anthraquinone, anthrone,and anthrone-like heterocycles (for example, heterocyclic analogs ofanthrone such as those having nitrogen, oxygen, or sulfur in the10-position), or their substituted (for example, ring substituted)derivatives. Examples of preferred aryl ketones include heterocyclicderivatives of anthrone, including acridone, xanthone, and thioxanthone,and their ring substituted derivatives. Particularly preferred arethioxanthone, and its derivatives, having excitation energies greaterthan about 360 nm.

The functional groups of such ketones are preferred since they arereadily capable of undergoing the activation/inactivation/reactivationcycle described herein. Benzophenone is a particularly preferred latentreactive moiety, since it is capable of photochemical excitation withthe initial formation of an excited singlet state that undergoesintersystem crossing to the triplet state. The excited triplet state caninsert into carbon-hydrogen bonds by abstraction of a hydrogen atom(from a support surface, for example), thus creating a radical pair.Subsequent collapse of the radical pair leads to formation of a newcarbon-carbon bond. If a reactive bond (for example, carbon-hydrogen) isnot available for bonding, the ultraviolet light-induced excitation ofthe benzophenone group is reversible and the molecule returns to groundstate energy level upon removal of the energy source. Photoactivatiblearyl ketones such as benzophenone and acetophenone are of particularimportance inasmuch as these groups are subject to multiple reactivationin water and hence provide increased coating efficiency.

In other embodiments, the photoreactive moiety is pendent from thepolymeric material. For example, at least one photoreactive group iscovalently bonded to the polymeric material. Polymeric material havingpendent photoreactive groups can be coupled to a component, such as thebiocompatible agent, or more than one moiety, by activating one or moreof the photoreactive groups of the polymeric material.

Preparation of polymeric material, biocompatible agents, or miscibilityenhancers having pendent photoreactive groups can be achieved by avariety of different methods. For example, a polymer (such as apolymeric miscibility enhancer) having pendent photoreactive groups canbe first prepared by preparing a copolymer and then reacting thecopolymer with compounds that lead to the photoderivitization of thecopolymer.

For example, an photoreactive polymer can be formed by reactingacrylamide, 2-acrylamide-2-methylpropane sulfonic acid, andN-3-aminopropyl)methacrylamide to form a copolymer. The copolymer isderivatized with an acyl chloride (such as, for example,4-benzoylbenzoyl chloride) under Schotten-Baumann conditions. That is,the acyl chloride reacts with the amino group of the N-(3-aminopropyl)moiety of the copolymer. An amide is formed resulting in the attachmentof the aryl ketone to the polymer.

Photo-poly(vinylpyrrolidone) (also referred to as “photo-PVP”) can beformed by the copolymerization of 1-vinyl-2-pyrrolidone andN-(3-aminopropyl(meth)acrylamide), which then can be derivatized with anacyl chloride (such as, for example, 4-benzoylbenzoyl chloride) underSchotten-Baumann conditions. That is, the acyl chloride reacts with theamino group of the N-(3-aminopropyl) moiety of the copolymer. An amideis formed resulting in the attachment of the aryl ketone to the polymer.Photo-PVP is commercially available, from SurModics, Inc., Eden Prairie,Minn., or can be synthesized.

Photoderivatized polysaccharides, such as heparin (“photoheparin”) canbe prepared by those skilled in the art as well, for example, in themanner described in U.S. Pat. No. 5,563,056 (Swan et al., see Example4), which describes the preparation of photoheparin by reacting heparinwith benzoyl-benzoyl-epsilon-aminocaproyl-N-oxysuccinimde indimethylsulfoxide/carbonate buffer. The solvent was evaporated and thephotoheparin was dialyzed against water, lyophilized, and then dissolvedin water.

Other photoderivatized biocompatible agents, such as collagen,fibronectin, and laminin can be prepared as described. See, for example,U.S. Pat. No. 5,744,515 (Clapper, Method and Implantable Article forPromoting Endothelialization). As described in this patent, aheterobifunctional crosslinking agent can be used to photoderivatize aprotein, such as a biocompatible agent. The crosslinking agent includesa benzophenone photoactivatable group on one end (benzoyl benzoic acid,BBA), a spacer in the middle (epsilon aminocaproic acid, EAC), and anamine reactive thermochemical coupling group on the other end(N-oxysuccinimide, NOS). BBA-EAC is synthesized from 4-benzoylbenzoylchloride and 6-aminocaproic acid. Then the NOS ester of BBA-EAC issynthesized by esterifying the carboxy group of BBA-EAC by carbodiimideactivation with N-hydroxysuccimide to yield BBA-EAC-NOS. Proteins, suchas collagen, fibronectin, laminin, and the like can be obtained fromcommercial sources. The protein is photoderivatized by adding theBBA-EAC-NOS crosslinking agent at a ratio of 10-15 moles of BBA-EAC-NOSper mole of protein.

Typically, the reacted photogroups present in the biocompatible layercouple one or more components present in the coating together. Forexample, in some embodiments, the reacted photogroups can couple thebiocompatible polymer to the hydrophobic polymer and/or PVP, and/or cancouple the PVP polymer to the biocompatible polymer and/or thehydrophobic polymer. The biocompatible coating can be formed with thereactive photogroups being pendent from one or more of the polymericcomponents (and bonded to another coated component), the reactedphotogroups being independent of any component in the coatingcomposition, or both. In a preferred aspect the coating composition isformed using reactive photogroups that are pendent from thebiocompatible polymer, the PVP polymer, and most preferably both thebiocompatible polymer and the PVP polymer.

In yet other embodiments the photoreactive moiety is independent of thebiocompatible polymer and the polymeric material. For example, thephotoreactive moiety can be a molecule having at least one photoreactivegroup that is able to couple the biocompatible polymer to the polymericmaterial when activated. One example is a crosslinking agent thatincludes two or more photoreactive groups.

Preferred activated photogroups are selected from activated arylketones, for example, activated benzophenone.

In order to provide a preferred coating, a coating composition can beprepared to include a solvent or dispersant, polymeric material that caninclude one or more polymers, the biocompatible agent, the bioactiveagent(s), and the photoreactive moiety. Solvents or dispersant that canbe included in the coating composition include, but are not limited to,alcohols (e.g., methanol, ethanol, n-propanol and isopropanol), alkanes(e.g., halogenated or unhalogenated alkanes such as hexane, heptane,cyclohexane, methylene chloride and chloroform), amides (e.g.,dimethylformamide, N-methylpyrrolidone), ethers (e.g., tetrahydrofuran(THF), dipropyl ether and dioxolane), ketones (e.g., methyl ethylketone, methyl isobutyl ketone), aromatic compounds (e.g., toluene andxylene), nitriles (e.g., acetonitrile), and ester (e.g., ethyl acetateand butyl acetate).

In another aspect of the invention, it has been found that isopropanolis particularly useful as a component in the coating composition. It hasbeen found that solutions or suspensions of the adherent polymer and thebiocompatible agent, and also the miscibility enhancer, can be preparedthat include isopropanol and then mixed together in order to prepare thecoating composition. For example, isopropanol can be present in anamount of 50% or greater, 60% or greater, 70% or greater, 80% orgreater, or most preferably 85% or greater of the amount of solvent ordispersant present in the composition (volume/volume). Isopropanol canbe present in combination with other solvents or dispersants, forexample water or THF. In some embodiments, the solvents include amixture of isopropanol, water, and THF. In some embodiments isopropanolis present in an amount of 85% or greater, water is present in an amountof 1% or greater, and THF is present in an amount of 1% or greater ofthe total solvents.

Therefore, in yet another aspect, the invention provides a coatingcomposition comprising (a) heparin, (b) a polymeric material comprisingmonomeric units selected from alkyl acrylates and alkyl methacrylates,and (c) photoreactive moiety, wherein the photoreactive moiety is eithercoupled to (a), (b), both (a) and (b), or is independent; andisopropanol. In some embodiments, the coating composition can alsoinclude tetrahydrofuran.

In one preferred method for preparing the coating composition, solutionsof the polymeric components are individually prepared and then combined.In a first solution, the hydrophobic polymer, preferably apoly(alkyl(meth)acrylate) such as poly(butyl(meth)acrylate), isdissolved or suspended in a solvent selected from the group consistingof tetrahydrofuran (THF) and acetone. Most preferably the hydrophobicpolymer is dissolved in THF. In a second solution, a hydrophilicbiocompatible polymer, preferably a biocompatible polysaccharide such asheparin, is dissolved or suspended in a protic solvent, preferablywater. In third solution poly(vinylpyrrolidone) is dissolved orsuspended in a solvent selected from the group consisting of water,diethylene glycol, methanol, ethanol, n-propanol, isopropanol (IPA),n-butanol, chloroform, methylene chloride, 2-pyrrolidone, polyethyleneglycol, propylene glycol, 1,4-butanediol, glycerol, triethanolamine,propionic acid, and acetic acid; in a preferred aspect the solvent isIPA.

Next, the second solution (hydrophilic biocompatible polymer) solutionand the third solution (PVP) are combined to form a mixture; thismixture is then added to the first solution (hydrophobic polymer).

In some aspects, the invention provides a coating composition includingpolymeric components comprising (i) a hydrophobic polymer, preferably apoly(alkyl(meth)acrylate such as pBMA; (ii) a hydrophilic biocompatiblepolymer, preferably heparin; (iii) a PVP polymer; and (iv) photoreactivegroups, wherein the photoreactive groups are preferably pendent from(ii) or (iii), or both (ii) and (iii), and wherein the polymericcomponents are present solvent system comprising (a) a first liquidselected from tetrahydrofuran (THF) and acetone; and (b) a second liquidselected from water, diethylene glycol, methanol, ethanol, n-propanol,isopropanol (IPA), n-butanol, chloroform, methylene chloride,2-pyrrolidone, polyethylene glycol, propylene glycol, 1,4-butanediol,glycerol, triethanolamine, propionic acid, and acetic acid. Preferablythe second liquid is selected from C₁-C₄ alcohols such as methanol,ethanol, n-propanol, isopropanol (IPA), and n-butanol. Most preferablythe second liquid is IPA.

In a more preferred embodiment the polymeric components, as described,are present in a solvent system comprising (a) a first liquid selectedfrom tetrahydrofuran (THF) and acetone; and (b) a second liquid selectedfrom water, diethylene glycol, methanol, ethanol, n-propanol,isopropanol (EPA), n-butanol, chloroform, methylene chloride,2-pyrrolidone, polyethylene glycol, propylene glycol, 1,4-butanediol,glycerol, triethanolamine, propionic acid, and acetic acid, and (c)water.

In another preferred embodiment, the polymeric components are present ina solvent system comprising (a) a first liquid selected fromtetrahydrofuran (THF) and acetone; and (b) C₁-C₄ alcohols such asmethanol, ethanol, n-propanol, isopropanol (IPA), and n-butanol, and (c)water.

In another preferred embodiment, the polymeric components are present ina solvent system comprising (a) tetrahydrofuran; and (b) isopropanol(IPA), and (c) water.

The first liquid (i.e., TBF or acetone) is preferably present in thesolvent system at a concentration of 50% or greater, preferably in therange of 50% to 90%, and even more preferably in the range of about 60%to about 80%. Preferably the first liquid is THF.

The second liquid, if, for example, present in a binary solvent systemwith the THF or acetone, is present at a concentration of 50% or less,preferably in the range of 50% to 10%, and even more preferably in therange of about 40% to about 20%.

A most preferred solvent system includes a (i) first liquid selectedfrom THF or acetone present in the solvent system at a concentration of50% or greater, preferably in the range of 50% to 90%, and even morepreferably in the range of about 60% to about 80%; a second liquidselected from diethylene glycol, methanol, ethanol, n-propanol,isopropanol (IPA), n-butanol, chloroform, methylene chloride,2-pyrrolidone, polyethylene glycol, propylene glycol, 1,4-butanediol,glycerol, triethanolamine, propionic acid, and acetic acid, present inthe solvent system at a concentration of 35% or less, preferably in therange of 5% to 30%; and water at a concentration of 20% or less, forexample, in the range of 0. 1% to 20%, more preferably in the range of0.1% to 2%. One example of a suitable ternary solvent system consists of60% THF, 25% IPA, and 15% water.

The polymeric components can be combined in any manner that would allowformation of a coating composition suitable for forming a biocompatiblelayer. However, it has been discovered that some methods of preparingthe biocompatible coating composition provide a biocompatible coatingcomposition that can be deposited on the surface of an article andprovide excellent biocompatible features.

In more specific aspects, the invention provides compositions havingpolymeric components present in amounts in defined ranges. Particularlyuseful ranges for the hydrophobic polymer, for example, thepoly(alkyl(meth)acrylate) polymer, are at concentrations in the range of1-20 mg/mL, more preferably in the range of 2.5-10 mg/mL, and mostpreferably in the range of 2.5-7.5 mg/mL

The hydrophilic biocompatible polymer (e.g., heparin) is preferablypresent in an amount of 0.1 mg/mL or greater, for example in the rangeof 0.1-10.0 mg/mL, and preferably in the range of 0.25 to 1.5 mg/mL.Particularly useful ranges for PVP is in the range of 0. 1-2.5 mg/mL,and preferably in the range of 0.1-1.0 mg/mL.

According to the invention, at least a portion of the surface of themedical article is coated with the coating composition. In someembodiments, the entire surface of the medical article can be coatedwith the coating composition. The amount of the surface area providedwith the polymeric material can be determined according to such factorsas the medical device to be utilized, the application of the device, thebioactive agent to be utilized with the polymeric material, and the likefactors.

Coating compositions described herein that include polymeric materialshaving any combination polymers, biocompatible agents, and desiredbioactive agents can be provided to the surface of the medical article,depending upon the final application of the medical device. The coatingcomposition (with or without bioactive agent) can be applied to themedical device using standard techniques to cover the entire surface ofthe device, or a portion of the device surface. Further, the coatingcomposition can be disposed on the medical article as a single layer(with or without bioactive agent) or in combination with other layers(with or without bioactive agent). When multiple layers are provided onthe surface, each individual layer can include one or more componentschosen to provide a desired effect. In some embodiments, each layer iscomposed of the same polymeric materials. Alternatively, one or more ofthe layers is composed of a polymeric material that is different fromone or more of the other layers. Additionally, multiple layers ofvarious bioactive agents can be deposited onto the medical devicesurface so that a particular bioactive agent can be presented to orreleased from the medical device at one time. Application techniques forthe coating of polymeric material include, for example, dipping,spraying, and the like. The suitability of the coating composition foruse with a particular medical article, and in turn, the suitability ofthe application technique, can be evaluated by those skilled in the art,given the present description.

In some aspects of the invention, the biocompatible layer comprises atleast three polymers. Of the three, the first polymer is a hydrophobicpolymer which can be selected from the group of poly(meth)acrylates. Ina preferred aspect the first polymer is a poly(alkyl(meth)acrylate)having a short chain, such as those in the range of C₂-C₅, includingpropyl (C₃), and most preferably butyl (C₄). Most preferably the firstpolymer is poly(butyl(meth)acryate) (pBMA). In some cases, andpreferably, the first polymer of the biocompatible layer can be the sameas the hydrophobic polymer of the bioactive agent-releasing layer. Forexample the hydrophilic polymer of the bioactive agent-releasing layerand the biocompatible layer is pBMA.

Therefore, in some aspects, the invention provides a method of providinga biocompatible bioactive agent releasing coating, the method includingthe steps of (a) disposing bioactive agent composition comprising abioactive agent and a hydrophobic polymer, preferably apoly(alkyl(meth)acrylate), on an article to form a bioactiveagent-releasing layer and (b) disposing a biocompatible coatingcomposition comprising (i) a hydrophobic polymer, (ii) a hydrophilicbiocompatible polymer, and (iii) PVP, wherein the photoreactive moietyis pendent from (ii) or (iii). In some cases the method of forming thecoating can include one or more other steps of forming a coated layerthat is different than the bioactive agent-releasing layer or thebiocompatible layer. These optional steps can include, for example, astep of forming a tie layer or a step of forming an intermediate layer.

In some cases the composition is pre-irradiated, that is, thecomposition is irradiated prior to being disposed on the surface of anarticle.

For example, a composition including photo-heparin and photo-PVP isirradiated to activate the photoreactive groups; subsequently thecomposition is disposed on the surface of the device. Therefore, in thispreferred aspect, a preferred method of coating comprises the steps of(a) providing a coating composition comprising (i) a hydrophobicpolymer, (ii) a hydrophilic biocompatible polymer, and (iii) PVP,wherein the photoreactive moiety is pendent from (ii) or (iii); (b)after step (a) treating the coating composition to activate thephotoreactive moiety, and (c) after step (b) disposing the coatingcomposition on the surface of the medical article. One or more othersteps can be include in this method which can be performed before,after, or in between steps (a)-(c).

In some cases, irradiation may occur before or after disposing thecoating composition.

In other aspects, the invention provides methods of providing abiocompatible coating to a surface of a medical article. The methodscomprise the steps of (a) providing a coating composition comprising (i)a hydrophobic polymer, (ii) a hydrophilic biocompatible polymer, and(iii) PVP, wherein the photoreactive moiety is pendent from (ii) or(iii); (b) disposing the coating composition on the surface of themedical article; and (c) treating the coating composition to activatethe photoreactive moiety. In a preferred aspect, the coating compositioncomprises a solvent system comprising (i) a first liquid selected fromTHF or acetone, (ii) IPA, and (iii) water.

In another aspect, the invention provides a coating composition that canbe used to form a layer that provides biocompatibility to all or aportion of a surface of an article. The coating composition includes atleast the components that are used to form a biocompatible layer on thesurface of an article.

In some aspects of the invention, the coating composition includes abioactive agent and the step of treating the composition is performedafter the coating composition is deposited on the surface of the medicalarticle. In these aspects a method comprising steps of determininginformation indicative of wavelength of light that causes inactivationof the bioactive agent, and using the wavelength information obtained toselect a filter for coupling photoreactive agents to the polymericmaterial containing the bioactive agent. According to these embodiments,inactivation of the bioactive agent means degradation of the bioactiveagent sufficient to reduce or eliminate the therapeutic effectiveness ofthe bioactive agent.

In some aspects of the invention, the methods and compositions can beparticularly useful for providing coatings to surfaces of medicaldevices, the coating providing features and that incorporates apolymeric material that can be deposited and adhered to a surface. Whileadhering to the substrate surface, the polymer of the coatingcomposition also allows the biocompatible agent to be stably presentedon the surface of the coated article. Since a treatment step is notnecessary after the coating composition is deposited on the surface ofthe substrate, this may allow a bioactive agent to be incorporated intothe coating composition without subjecting the bioactive agents to atreatment step, thereby reducing the possibility of degradation of thebioactive agents by the treatment.

In addition, the polymeric material of the coating composition can beuseful for controllably releasing one or more bioactive agents from thebiocompatible coating. A coating composition containing polymericmaterial having both adherent and drug-releasing properties and abiocompatible agent can be prepared. After the composition is prepared abioactive agent can be incorporated into the composition. The coatingcomposition can be deposited on a substrate to provide a biocompatibleand drug-releasing coating.

A coating with these properties can surprisingly be formed on a surfaceof a medical device in a minimal number of steps. This greatly reducesthe throughput time for the fabrication of medical articles having thesefeatures and can result in a substantial cost savings as many reagentsand steps that might typically be attempted in fabrication of thesecoated medical articles are not necessarily required.

The compositions and methods of the invention provided coatings thatwere readily prepared and that demonstrated excellent biocompatible andwettability characteristics. For example, stents coated withcompositions according to the invention demonstrated substantial heparinor collagen surface activities.

In preferred embodiments, the coating composition includes a bioactiveagent or the method of coating further comprises a step of adding abioactive agent to the coating composition. In some aspects thebioactive agent is added to the coating composition after the step oftreating the coating composition has been performed. The bioactive agentcan be released from or presented by the coating once the coating isformed on the medical article and implanted in a patient. In someembodiments, the coating composition can include more than one bioactiveagent, wherein each of the bioactive agents can be independentlyselected depending upon the desired therapeutic application of theinvention.

In the step of treating, the photoreactive moieties can be activated byirradiation using a suitable light source. In some aspects of theinvention, photoreactive group can be activated using a filtered lightsource. A useful filtered light source provides wavelengths of lightthat are greater than the wavelength at which the bioactive agentmaximally absorbs light.

In some embodiments, the coating composition includes a bioactive agentor the method further comprises a step of adding a bioactive agent tothe coating composition. In some aspects the bioactive agent is added tothe coating composition after the step of treating the coatingcomposition has been performed. The invention contemplates variousembodiments for forming a biocompatible coating, also including abioactive agent, some of which are now described in greater detail.

In another particular aspect of the invention, the method includes thesteps of (a) providing a coating composition comprising a polymerselected from the groups consisting of includespoly(alkyl(meth)acrylates) and poly(aromatic(meth)acrylates) and abiocompatible agent comprising at least one photoreactive moiety; (b)treating the coating composition to activate the photoreactive group;(c) adding a bioactive agent to the coating composition; and (d)disposing the coating composition on the surface of the medical article.

In another particular aspect of the invention, the method includes thesteps of (a) providing a coating composition comprising an adherentpolymer and a biocompatible agent comprising at least one photoreactivemoiety; (b) treating the coating composition to activate thephotoreactive group; (c) adding a bioactive agent to the coatingcomposition; and (d) disposing the coating composition on the surface ofthe medical article.

In another particular aspect of the invention, the method includes thesteps of (a) providing a coating composition comprising an adherentpolymer and a polysaccharide comprising at least one photoreactivemoiety; (b) treating the coating composition to activate thephotoreactive group; (c) adding a bioactive agent to the coatingcomposition; and (d) disposing the coating composition on the surface ofthe medical article.

In another particular aspect of the invention, the method includes thesteps of (a) providing a coating composition comprising an adherentpolymer and a protein or peptide comprising at least one photoreactivemoiety; (b) treating the coating composition to activate thephotoreactive group; (c) adding a bioactive agent to the coatingcomposition; and (d) disposing the coating composition on the surface ofthe medical article.

In another particular aspect of the invention, the method includes thesteps of (a) providing a coating composition comprising a polymer havingalkyl acrylate or alkyl methacrylate monomeric units and a biocompatibleagent comprising at least one photoreactive moiety; (b) treating thecoating composition to activate the photoreactive group; (c) adding abioactive agent to the coating composition; and (d) disposing thecoating composition on the surface of the medical article.

In another particular aspect of the invention, the method includes thesteps of (a) providing a coating composition comprising a polymer havingalkyl acrylate or alkyl methacrylate monomeric units, and heparincomprising at least one photoreactive moiety; (b) treating the coatingcomposition to activate the photoreactive group; (c) adding a bioactiveagent to the coating composition; and (d) disposing the coatingcomposition on the surface of the medical article.

In another particular aspect of the invention, the method includes thesteps of (a) providing a coating composition comprising a polymer havingalkyl acrylate or alkyl methacrylate monomeric units, and collagencomprising at least one photoreactive moiety; (b) treating the coatingcomposition to activate the photoreactive group; (c) adding a bioactiveagent to the coating composition; and (d) disposing the coatingcomposition on the surface of the medical article.

The invention contemplates various embodiments for forming abiocompatible coating, wherein the presence of a bioactive agent isoptional, but not required. Alternatively, in some aspects a bioactiveagent can be disposed before or after disposing the biocompatiblecoating composition.

In another embodiment, the method includes the steps of (a) providing acoating composition comprising (i) an adherent polymer, (ii) miscibilityagent selected from the group consisting of polyvinylpyrrolidinone(PVP), polyethyleneglycol (PEG), PEG sulfonates, fatty quaternaryamines, fatty sulfonates, fatty acids, dextran, dextrin, andcyclodextrin, (iii) a biocompatible agent, and (iv) a photoreactivemoiety, and wherein the photoreactive moiety is pendent from (i),pendent from (ii), pendent from (iii), independent, or combinationsthereof; (b) disposing the coating composition on the surface of themedical article; and (c) treating the coating composition to activatethe photoreactive group.

In another particular embodiment, the method includes the steps of (a)providing a coating composition comprising (i) an adherent polymer, (ii)polyvinylpyrrolidone, (iii) a biocompatible agent, and (iv) aphotoreactive moiety, and wherein the photoreactive moiety is pendentfrom (i), pendent from (ii), pendent from (iii), independent, orcombinations thereof; (b) disposing the coating composition on thesurface of the medical article; and (c) treating the coating compositionto activate the photoreactive group.

In some aspects, an outer coating (“topcoat”) of biocompatible agent canbe applied to the coated composition. The outer coating can be providedon a portion of, or the entirety of, the medical article surface.

In the step of treating, the photoreactive moieties can be activated byirradiation using a suitable light source. In some aspects of theinvention, photoreactive group can be activated using a filtered lightsource. A useful filtered light source provides wavelengths of lightthat are greater than the wavelength at which the bioactive agentmaximally absorbs light.

In some embodiments, a filter is utilized in connection with the step oftreating, which can involve the activation of the one or morephotoreactive groups. In embodiments wherein a bioactive agent isincluded in the coating composition, the one or more photoreactivegroups are activated by providing light having a wavelength selected ina range to activate the photoreactive groups and minimize inactivationof bioactive agent in the polymeric material.

In one such embodiment, for example, a medical article having apolymeric material disposed on at least a portion of its surface isprovided, wherein the polymeric material includes a bioactive agent. Inone illustrative example, the bioactive agent is an analog of rapamycin(also referred to herein as a “rapalog”). It can be determined thatrapamycin is inactivated at wavelengths in the range of 300 nm or less.This information can be utilized in combination with informationrelating to electromagnetic energy sufficient to activate photoreactiveagents (for example, to undergo active specie generation with resultantcovalent bonding to an adjacent chemical structure) as described herein(for example, having activation wavelengths in the UV and visibleportions of the spectrum, such as in the range of 100-700 nm, or 300-600nm, or 200-400 nm, or 300-340 nm). The combined information can then beutilized to select an appropriate light filter for application ofphotoreactive species to the polymeric material.

Information relating to the UV spectra at which a particular bioactiveagent is degraded can be obtained, for example, by the provider of thebioactive agent, or by subjecting the bioactive agent to a variety ofwavelengths of light, and determining the subsequent activity retainedof the bioactive agent.

Typically, filters are identified by the wavelength of light that ispermitted to pass through the filter. Two illustrative types of filtersthat can be used in connection with the invention are cut-off filtersand band pass filters. Generally, cut-off filters are categorized by acut-off transmittance, at which the light transmittance is approximately25% of the maximum transmittance. For band pass filters, a range ofwavelength is identified for the filter, and the center wavelength isthe midpoint of wavelength allowed through; at midpoint, thetransmittance is approximately half of the maximum transmittance allowedthrough the filter.

Thus, in one embodiment utilizing a band pass filter, for example, anEdmund 407 nm filter, the filter can be chosen that has a maximum UVtransmittance at its center wavelength of 407 nm. From either directionfrom that, the UV transmittances decreases. Thus, towards 300 run, theUV transmittance is not enough to cause significant degradation of therapalog. This filter can be selected and utilized to couple aphotoreactive reagent to a polymeric material containing rapamycin or arapalog, as shown in the Examples. Other exemplary embodiments of thisaspect of the invention can be found in the examples.

The invention will be further described with reference to the followingnon-limiting Examples.

EXAMPLES

For the following examples, the following standard reagents andnomenclature are adopted:

Compound I (BBA-EAC-Heparin; Photo-Heparin)

Compound II (photo-polyvinylpyrrolidone copolymer; Photo-PVP)

Compound III (Acetylated PVP-APMA-BBA; Acetylated Photo-PVP)

Compound IV (Tetrakis (4-benzoylbenzyl ether) of pentaerythritol (TBBE)

Spray Coating

The following spray coating procedure was followed in order to deposit aheparin-containing composition on the stents. The coating procedure wasperformed in order to provide stents with a desired amount of solidsfrom the photo-heparin composition.

The parts were placed on a roller system such as that described in U.S.patent application Ser. No. 10/256,349 (“Advanced Coating Apparatus andMethod,” Chappa et al., filed Sep. 27, 2002). The device rotatorincluded a pair of rollers suitable for holding the stent, the pairhaving first and second rollers arranged substantially parallel to eachother and separated by a gap. The spray nozzle was operationallyarranged to produce spray of a coating material directed at the gap and,when the device is not positioned on the pair of rollers, arranged sothe majority of the spray was passed through the gap. In use, aheparin-containing composition was disposed on the device from the spraynozzle, and the majority of any spray that did not get deposited on thedevice was passed through the gap. The stent was then rotated byrotation of the rollers to position a different portion of the devicefor subsequent application of the heparin-containing composition.Coating was applied to the stent at a rate of 0.5 mL/min (or at a ratein the range of 0.03-0.1 mL/min as indicated). The spray nozzle utilizedwas an ultrasonic nozzle operated at a power of 0.6 W (unless otherwisenoted), such as that commercially available from Sonotek (Ultrasonicspray coater) and described in U.S. patent application Ser. No.10/256,349. The coating parameters were as follows. The spray nozzlemoved over stents at a rate of 50-150 mm/sec. The spray head passed overthe stent 10-120 times (Examples 1-5) or 150-320 times (Examples 7-13)(described as the number of “passes”; 2 passes equals 1 cycle), asindicated. The total number of passes was selected to provide a finalcoated weight of heparin in the range of 5-10 μg/stent, and a finalheparin-containing layer weight in the range of 50-150 μg. Also, thestent was rotated during the spray coating process a sufficient numberof times to provide a uniform coating on the surface (typically, thestent was rotated a minimum of 2 revolutions per coating application).In some cases, where indicated, a 20% speed pause was implemented aftereach cycle. The spray coatings were applied in a low humidityenvironment (less than 5% humidity). The coating solution was suppliedfrom the spray nozzle at a pressure at 2 psi unless otherwise noted.

Heparin Activity Assay

The antithrombotic activity of heparin is due to its inhibition ofthrombin, which is a protease that is known to participate in theclotting cascade. Heparin inhibits thrombin activity by first binding toantithrombin mi (ATE). The heparin/ATIII complex then binds to andinactivates thrombin, after which the heparin is released and can bindto another ATIII. The assay for inhibition of thrombin by immobilizedheparin was conducted by measuring the cleavage of a chromogenic peptidesubstrate by thrombin.

Prior to performing the Heparin Activity Assay, coated stents werewashed overnight (12-18 hours) to remove any unbound material from thecoated stents. Coated stents were washed in diH₂O or PBS at atemperature of about 37° C. on an orbital shaker (set for gentleagitation).

Each assay was conducted in 1 mL of PBS that contained 0.85 mg BSA(Sigma Chemical Co.), 10 mU human thrombin (Sigma Chemical Co.), 100mU/mL ATIII (Baxter Biotech, Chicago, Ill.), and 0.17 μmole of thechromogenic thrombin substrate S-2238 (Kabi Pharmacia, Franklin, Ohio).To this assay solution was added either uncoated or heparin coatedstents (to evaluate heparin activity on the membranes) or standardconcentrations of heparin (to generate standard curves of heparincontent versus absorbance). For standard curves, the amounts of heparinthat were added ranged from 2.5 mU to 25 mU. The color generated,measured as absorbance at 405 nm, by thrombin mediated cleavage of theS-2238 was read using a spectrophotometer after 2 hours of incubation at37° C. The absorbance was directly related to the activity of thethrombin and, thus, inversely related to the amount of activation ofATIII induced by the heparin in solution or immobilized on the surfaceof the substrate. Activity of surface bound heparin was calculated bycomparing the absorbance values generated with the membranes to theabsorbance values generated with known amounts of added heparin.Commercial preparations of heparin are commonly calibrated in USP units,1 unit being defined as the quantity that prevents 1.0 mL of citratedsheep plasma from clotting for 1 h after the addition of 0.2 mL of 10g/L CaCl₂ (see Majerus PW, et al. Anticoagulant, thrombolylic, andantiplatelet drugs. In: Hardman J G, Limbrid L E, eds., Goodman andGilman's The pharmacological bases of therapeutics, 9th ed, New York:McGraw Hill, 1996:1341-6). Commercial preparations of heparin typicallyinclude the heparin activity of the preparation. In order to determinethe heparin activity of a heparin coating described herein, the aboveassay can be performed and compared to a standard generated from acommercial preparation of heparin, based on the above definition ofheparin activity.

For all examples, 1-7 stents had a surface area of 0.8757 cm².

Example 1

Coating composition premixtures containing pBMA(poly(butyl)methacrylate); and photo-heparin (Compound I) were preparedand coated on stainless steel stents, demonstrating that a medicalarticle having a coating containing an adhesion polymer and havingbiocompatible properties can be prepared in a process that requires aminimum number of steps.

Solutions of pBMA at a concentration of 10 mg/ml in 90% THF, 10% H₂O,and a solution of pBMA at a concentration of 10 mg/ml in 100% THF wasprepared. Solutions of photo-heparin at concentrations of 5 mg/ml and 10mg/ml in 90% THF 10% H₂O, and a solution of photo-heparin at 50 mg/ml inH₂O was prepared. For a control, a solution of heparin (non-photo) at 50mg/ml in H₂O was prepared. At these concentrations the pBMA andphoto-heparin did not precipitate out of solution. The solutions of pBMAand photoheparin were mixed in order to prepare mixtures having thefollowing concentrations of pBMA and photo-heparin:

(A) 5 mg/ml photo-heparin; 2.5 mg/ml pBMA

(B) 5 mg/ml photo-heparin; 10 mg/ml pBMA

(C) 5 mg/ml heparin (non-photo); 10 mg/ml pBMA

The percentage of solvents in mixtures (A)-(C) was 90% THF, 10% H₂0.

Mixtures (A)-(C) were disposed on stents using the spray coatingtechnique described herein. In some samples (1-B3/B4 and 1-C3/C4, seeTable 1) the coated stents were subject to irradiation for 45 seconds at6-8 mW/cm² using a 324 nm filter. In other samples no irradiation wasperformed. TABLE 1 Heparin Sample Irradiation after Surface activity No.spray coating Characteristic (mU/cm²) 1-A1 Yes Dewet 29 1-A2 Yes Dewet17 1-B1 Yes Dewet 26 1-B2 Yes Dewet 27 1-B3 No Dewet nr 1-B4 No Dewet nr1-C1 Yes Dewet  6 1-C2 Yes Dewet  2 1-C3 No Dewet nr 1-C4 No Dewet nrnr = not recorded

Heparin activity was shown on the surface of stents coated with pBMA andphotoheparin (at two different concentrations (1-A1/A2 and 1-B1/B2) thatwere also subject to an irradiation step. Stents not receiving a dose ofUV irradiation (1-B3/B4 and 1-C3/C4), or stents that receivedirradiation but had a coating that included non-photo heparin (1-C1/C2)demonstrated little or no surface heparin activity.

Example 2

Coating composition premixtures containing pBMA, photo-heparin, andacetylated-photo-PVP (Compound III) were prepared and coated onstainless steel stents. The stents had coatings that demonstratedexcellent biocompatibility properties.

A mixture of pBMA at a concentration of 5 mg/ml, photo-heparin at 2.5mg/ml, and photo-polyvinylpyrrolidone at 0.25 mg/ml in 90% THF and 10%H₂0 was prepared (Table 2).

Stents were coated using the spray coating apparatus having a pair ofrollers and an ultrasonic nozzle (as described herein) at rate of 0.03ml/min, 20% speed, and 1 psi. 20-50 μg of mixture was coated onto eachstent.

After the coating was performed the stents were: not subject to anirradiation step (2-A1/A2), subject to UV irradiation for 45 seconds at6-8 mW/cm² using a 324 nm filter (2-A3/A4), or subject to UV irradiationin addition to receiving a top coat of photo-heparin (2-A5/A6). Aheparin top coat was applied to the stents (50 mg/ml photo-heparin inH₂0 applied by spray coating and then irradiated for 45 seconds).

Results of heparin activity for the coated stents are shown in Table 2.TABLE 2 Photo- Heparin Sample Irradiation after heparin activity No.coating topcoat (mU/cm²) 2-A1 No No 0 2-A2 No No 2 2-A3 Yes No 42 2-A4Yes No 41 2-A5 Yes Yes 41 2-A6 Yes Yes 40

High levels of heparin activity were shown on the surface of stentscoated with the pBMA/photo-heparin/photo-PVP mixture and that were alsotreated with UV irradiation (2-A3/A4 and A5/A6). Stents having highlevels of heparin activity were able to be prepared (2-A3/A4) without aheparin topcoat (2-A5/A6). Coated stents not receiving a dose of UVirradiation (2-A1/A2) demonstrated little or no surface heparinactivity.

Example 3

Coating composition premixtures containing photo-heparin and photo-PVPwere prepared and subject to UV irradiation. The irradiated premixturesof photo-heparin and acetylated photo-PVP were then added to a solutionof pBMA and the resulting mixtures were then coated on stents. Stentshaving surface heparin activity were able to be prepared withoutdirectly irradiating the stent surface.

In addition, the coating compositions were applied in an improvedcoating solution that included isopropanol alcohol.

A miscibility test was first performed to determine if isopropanolalcohol is suitable as a common liquid for preparing a mixture of pBMA,photo-heparin, and acetylated photo-PVP. pBMA was dissolved at aconcentration of 10 mg/ml in 80% isopropanol (IPA), 20% THF.Photo-heparin was dissolved at a concentration of 10 mg/ml in 90% EPA,10% H₂0. Acetylated photo-PVP was dissolved at a concentration of 10mg/ml in 100% IPA. To 7 mls of IPA was added each 1 ml of the pBMA,photo-heparin, and acetylated photo-PVP solutions. The solution wasslightly cloudy without any observable precipitate, demonstrating thatisopropanol can be included as a liquid to improve properties of acoating mixture.

Stents having surface heparin activity were prepared without subjectingthe coated stent to a treatment of UV irradiation as follows. First,premixtures of photo-heparin at a concentration of 7.5 mg/ml, andacetylated photo-PVP at 5.0 mg/ml in H₂0 were prepared and subject to UVirradiation for either 20 seconds (3-B1/B2) or 30 seconds (3-C1/C2) at6-8 mW/cm². Non-irradiated mixtures of photo-heparin and acetylatedphoto-PVP were also prepared (3-A1/A2). The irradiated mixture was thencombined with pBMA to give a coating mixture having 1 mg/ml pBMA,0.75mg/ml photo-heparin, and 0.5 mg/ml photo-PVP in 88% IPA, 10% H₂0, 2%THF. The coatings were then spray coated onto stainless steel stents asdescribed in Example 2 and then heparin activity was determined (resultsshown in Table 3). TABLE 3 Irradiation Irradiation Heparin Sample ofphoto-herparin/ after activity No. photo-PVP premix coating (mU/cm²)3-A1 No No 3 3-A2 No No 3 3-B1 Yes, 20 sec No 7 3-B2 Yes, 20 sec No 73-C1 Yes, 30 sec No 7 3-C2 Yes, 30 sec No 7

According to the results shown in Table 3, heparin activity on thesurface of stents that had a coating that included an irradiatedpremixture of photo-heparin and acetylated photo-PVP (3-B1/B2 and3-C1/C2) was more than two times the heparin activity as compared tostents having a coating wherein the photo-heparin and acetylatedphoto-PVP premixture was not irradiated (3-A1/A2).

Example 4

Stents were also prepared that included coatings as described in Example3, but in addition included steps of treating the coated surface with UVand adding a topcoat of photoheparin following the initial coating. BothParylene™-C and bare metal stents were able to be prepared havingcoatings with excellent heparin activity.

Coating mixtures as described above (used in the preparation of 3-A1/A2,3-B1/B2, and 3-C1/C2 of Example 3) were disposed on Parlene-C stents asdescribed and then treated with UV irradiation for one minute at 6-8mW/cm². A topcoat of heparin was then added to the stents to completethe preparation of samples 4-A1/A2, 4-B1/B2, and 4-C1/C2, respectively.TABLE 4 Irradiation of Heparin Sample photo-heparin/ IrradiationPhoto-heparin activity No. photo-PVP premix after coating topcoat(mU/cm²) 4-A1 No Yes Yes 46 4-A2 No Yes Yes 47 4-B1 Yes, 20 sec Yes Yes49 4-B2 Yes, 20 sec Yes Yes 45 4-C1 Yes, 30 sec Yes Yes 46 4-C2 Yes, 30sec Yes Yes 48

Coating mixtures that included different photo-PVP polymers (acetylatedand non acetylated) and different concentrations of the photo-PVPpolymers were prepared and used to coat bare metal stents. The followingcoating compositions were prepared:

(4-D1/D2) 1 mg/ml pBMA, 1 mg/ml photo-heparin, and 1 mg/ml acetylatedphoto-PVP in 90% IPA, 10% H₂0.

(4-E1/E2) 1 mg/ml pBMA, 1 mg/ml photo-heparin, and 1 mg/ml photo-PVP(non acetylated) in 90% EPA, 10% H₂0.

(4-F1/F2) 1 mg/ml pBMA, 1 mg/ml photo-heparin, and 0.2 mg/ml photo-PVP(non acetylated) in 90% EPA, 10% H₂0.

(4-G1/G2) 1 mg/ml pBMA, 1 mg/ml photo-heparin in 90% IPA, 10% H₂0.

Coating mixtures (K)-(M) were disposed on bare metal stents using spraycoating and then treated with UV irradiation for one minute at 6-8mW/cm². A topcoat of heparin (in 10 mg/ml in 80% IPA, 20% H₂0) was thenadded to the stents. TABLE 5 Sample Irradiation Photo-heparin Heparinactivity No. after coating topcoat (mU/cm²) 4-D1 Yes Yes 45 4-D2 Yes Yes44 4-E1 Yes Yes 46 4-E2 Yes Yes 46 4-F1 Yes Yes 45 4-F2 Yes Yes 46 4-G1Yes Yes 29 4-G2 Yes Yes 31

Results from Table 5 demonstrate that the coating composition andmethods can provide bare metal stents with an excellent heparin surfaceactivity and that different miscibility enhancers can be used to preparesurfaces having excellent heparin surface activity.

Example 5

Coating composition premixtures containing photo-heparin, photo-PVP, andpBMA are prepared and subject to UV irradiation. The irradiatedpremixtures of photo-heparin, photo-PVP, and pBMA are then coated onstents.

Stents having surface heparin activity are prepared without subjectingthe coated stent to a treatment of UV irradiation as follows. First,premixtures of 1 mg/ml pBMA, 0.5 mg/ml photo-heparin, and 0.75 mg/mlphoto-PVP in 90% IPA, 10% H₂0 are prepared and dried. The driedpremixture is then irradiated and subject to UV irradiation. Thecoatings are then resuspended in IPA/H₂0 and then coated onto stainlesssteel stents as described in Example 2.

Example 6

Coating composition premixtures containing photo-collagen and pBMA wereprepared and disposed on metal flats and then subject to UV irradiation.To determine collagen activity, a cell attachment assay was performed byincubating PA-1 cells with the coated flats and determining celladherence. Very good collagen activity was achieved using premixtures ofphoto-collagen and pBMA.

Stainless steel flats (31 6L; 1×3 cm) were coated using the ultrasonicspray coater as described herein using a grid type pattern to coat theflats. The following compositions were coated on the flats:

(6-A) 1 mg/ml pBMA in 90% EPA, 10% H₂0.

(6-B) 0.3 mg/ml photo-heparin in 90% IPA, 10% H₂0.

(6-C) 0.4 mg/ml pBMA, 0.3 mg/ml photo-collagen in 90% EPA, 10% H₂0.

(6-D) 1 mg/ml pBMA, 0.3 mg/ml photo-collagen in 90% IPA, 10% H₂0.

(6-E) 2 mg/ml pBMA, 0.3 mg/ml photo-collagen in 90% IPA, 10% H₂0.

(6-F) 4 mg/ml pBMA, 0.3 mg/ml photo-collagen in 90% IPA, 10% H₂0.

(6-G) 4 mg/ml pBMA, 0.3 mg/ml photo-collagen in 90% IPA, 10% H₂0.

Sample (6-F) was coated onto a metal flat having a pBMA base coat.Sample (6-G) was coated onto a metal flat having a Parylene™ C basecoat. Tissue culture polystyrene and photocollagen on polystyrene(details) were used as controls.

Controls included uncoated tissue culture polystyrene (6-H) andphotocollagen immobilized on polystyrene (6-I). Photocollagen wasdiluted in 12 mM HCl to 200 ug/ml and incubated in wells of a tissueculture plate for one hour at room temperature; the well was thenilluminated for 90 seconds in a refrigerated illumination chamber with aDimax 365 nm lamp and then washed with PBS). The coated metal flats werethen mounted in the wells.

MEM (Modified Eagles Media) was added to each well (0.5 ml) andincubated at least 30 minutes at 37° C. and 5% CO₂. PA-1 cells wereadded to each well at a concentration of 150,000 cells/ml at 0.5 ml perwell in MEM (Modified Eagles Media) +2% BSA and incubated 90 minutes at37° C. and 5% CO₂. Media was then carefully removed from the wells andthe wells were gently rinsed with 1 ml of MEM to remove unattachedcells.

A chromogenic assay was performed to determine the number of cellsadhered to the coated metal flats. A solution of MTT at 5 mg/ml in PBSwas prepared and sterile filtered. A mixture of media/MTT was preparedby adding 5 ml of fresh media to 1.2 ml of the MTT preparation. Afterthe cells were rinsed 0.5 ml of the media/MTT mixture was added to eachwell and then incubated for 90 minutes at 37° C. and 5% CO₂. Themedia/MTT mixture was then removed with the flats and transferred to newwells. The dye was solubilized with 0.5 ml of 0.04 N HCl/isopropanol and0.12 ml 3% SDS/H₂O. Plates were shaken at room temperature at 100 rmpuntil the dye was completely solubilized and uniformly mixed. 200 ulaliquot samples were transferred in duplicate into 96 well plates andthe absorbance of the solution at 570 nm was determined.

Results are shown in Table 6. TABLE 6 Sample No. A570 6-A 0.020 6-B0.025 6-C 0.040 6-D 0.080 6-E 0.050 6-F 0.060 6-G 0.055 6-H 0.015 6-I0.135

As shown in Table 6, substrates coated with mixtures of pBMA andphotocollagen gave surfaces that allowed for greater cell adhesion thanthe pBMA-coated or photocollagen surfaces alone. In addition, mixturesof pBMA and photocollagen were able to coat surfaces already having alayer of either pBMA or photocollagen alone and provide these surfaceswith very good cell adhesive properties. Surfaces coated with a mixtureof pBMA at 1 mg/ml and photocollagen at 0.3 mg/ml had particularly goodcell adhesive properties.

Substrates (Examples 7-13)

18 mm×6 cell cobalt chromium stents having a surface area of 1.0 cm²were used as substrates, unless otherwise indicated, for coatingprocedures.

The cobalt chromium stents were prepared for coating by soaking in acleansing solution of ENPREP (ENTHOME-OMI, Inc.) at a concentration of60 mg/mL in DI water at a temperature of approximately 80° C. forapproximately 1 hour. After soaking, the stents were rinsed twice indistilled water for about 10 seconds each and then rinsed with IPA twicefor 10 seconds each. After rinsing, the stents were immersed in a silanesolution as indicated below.

Coating Materials and Method for Forming Coated Layers (Examples 7-13)

For purposes of discussion in the Examples 7-13, the following materialswere used to form coated layers on the surface of the stents unlessotherwise indicated:

(I) Silane layer. A silane layer was formed on the stents by immersingthe (bare metal) cleansed cobalt chromium stents in a solution of 0.5%(w/v) γ-methacryloxypropyltrimethyl-silane in a mixture of IPA/water atroom temperature for approximately 1 hour with shaking on an orbitalshaker. After silane treatment, the stents were briefly rinsed in IPAand then baked in an oven at a temperature of 100° C. for approximately1 hour.

(II) Parylene™ C layer. To form the Parylene™ layer, the silane-coatedstents by were placed in a Parylene™ coating reactor (PDS 2010 LABCOTER™2, Specialty Coating Systems, Indianapolis, Ind.) and coated withParylene™ C (Specialty Coating Systems, Indianapolis, Ind.) by followingthe operating instructions for the LABCOTER™ system. The resultingParylene™ C coating was approximately 1-2 μm thickness.

(III) pBMA/pEVA/rapamycin layer. For preparing the pBMA/pEVA/rapamycinlayer, a mixture of pEVA (33 weight percent vinyl acetate; AldrichChemical, Milwaukee, Wis.) at a concentration of 1.67 mg/ml; pBMA(337,000 average molecular weight; Aldrich Chemical, Milwaukee, Wis.) ata concentration of 1.67 mg/ml; and rapamycin (Sirolimus, Wyeth) at aconcentration of 1.67 mg/ml, was prepared in THF. ThepBMA/pEVA/rapamycin solution was sprayed onto the Parylene™ C treatedstents using an IVEK sprayer (IVEK Dispenser 2000, IVEK Corp., NorthSpringfield, Vt.) having a nozzle with a 1.0 mm (0.04 inch) diameterorifice and pressurized at 421.84 g/cm² (6 psi). The distance from thenozzle to the stent surface during coating application was in the rangeof 5 cm to 5.5 cm. A coating application consisted of spraying 40 μL ofthe coating solution back and forth on the stent for 7 seconds. Thespraying process of the coating was repeated until a desired amount ofdrug was present on the stents. The coating compositions on the stentwere dried by evaporation of solvent, approximately 8-10 hours, at roomtemperature (approximately 20° C. to 22° C.). After drying, the coatedwires were re-weighed. From this weight, the mass of the coating wascalculated, which in turn permitted the mass of the coated polymer(s)and bioactive agent to be determined. The compositional details aresummarized as a ratio of the weight percentages of the solid componentsin the composition.

(IV) pBMA layer. For preparation of the pBMA layer, a solution pBMA(337,000 average molecular weight; Aldrich Chemical, Milwaukee, Wis.) ata concentration of 2.5 mg/ml; was prepared in THF. The pBMA solution wassprayed onto the coated stents using an IVEK sprayer (IVEK Dispenser2000, IVEK Corp., North Springfield, Vt.) mounting a nozzle with a 1.0mm (0.04 inch) diameter orifice and pressurized at 421.84 g/cm² (6 psi).The distance from the nozzle to the stent surface during coatingapplication was in the range of 5 cm to 5.5 cm. A coating applicationconsisted of spraying 40 μL of the coating solution back and forth onthe stent for 7 seconds. The spraying process of the coating wasrepeated until a desired amount of drug was present on the stents. Thecoating compositions on the stent were dried by evaporation of solvent,approximately 8-10 hours, at room temperature (approximately 20° C. to22° C.). After drying, the coated wires were re-weighed.

(V) Heparin-containing layer. Coating compositions were prepared thatconsisted of various combinations of some or all the followingmaterials:

-   -   pBMA    -   photo-PVP (Compound II)    -   photo-heparin (Compound I) or heparin    -   photo-crosslinker

Preparation of the pBMA/photo-PVP/photo-heparin mixture in a ternarysolvent system (THF/IPA/H₂0) was carried out in a sequential manner. Thefollowing solutions were prepared at room temperature:

(i) pBMA at 50 mg/mL in THF

(ii) photo-PVP at 50 mg/mL in IPA

(iii) photo-heparin at 50 mg/mL in H₂0

In order to prepare a 10 mL of a heparin coating solution containing:pBMA (5.0 mg/mL)/photo-PVP (0.3125 mg/mL)/photo-heparin (0.625 mg/mL) ina final solution of 80% THF/5% IPA/15% H₂0, the following procedure wasperformed.

Solution (i) was diluted in THF by adding 1 mL of (i) to a mixture of 7mL of THF and 0.4375 mL of IPA. Next, a photo-PVP/photo-heparin mixturewas prepared by adding 62.5 μl of solution (ii) and 125 μl of solution(iii) into 1.375 mL of H₂0. (Optionally, photo-PVP and photo-heparin canbe individually dissolved in water and added to the mixture). Themixture of (ii) and (iii) was then shaken briefly at room temperature.The photo-PVP/photo-heparin mixture was then added to the pBMA solution.Various heparin coating solutions were prepared in this sequentialmanner having the following solvents present in these ranges:

-   -   THF: 20% -80% final    -   IPA: 5% -75% final    -   H₂0: 5% -20% final

Preparation of pBMA/photo-PVP/photo-heparin mixtures in a binary solventsystem (IPA/H20) or (THF/H₂0) was carried out in a sequential manner byfirst preparing solution of pBMA in IPA or THF, and then adding amixture of photo-PVP and photo-heparin dissolved in water to the pBMAsolution.

In some cases, coating compositions were prepared by substitutingheparin (not photo-derivitized) for photo-heparin.

Rapamycin Analysis—Drug Content Method by HPLC

Rapamycin content and quality from coated stent samples were analyzed byimmersing the (18 mm) coated stents into a glass test tube filled with 5mL acetonitrile, which dissolves coated material, including rapamycin,from the cobalt chromium stent surface. The tube was capped and shakenfor 30-45 minutes using a mechanical shaker. After shaking, a portion ofthe acetonitrile sample (having the eluted rapamycin) was sampled byHPLC using the following parameters:

Column: Supelco Hypersil BDS C18, 5 μm, 4.6×250

Temp: 40° C.

Mobile phase: 1,4-dioxane:water (3:2 v:v; mixed and degassed by H₂sparging)

Flow rate: 0.8±0.1 mL/min

Detection λ: 225nm

Injection volume: 25 μL

Run time: 40 min.

The HPLC column was equilibrated with the mobile phase solution(1,4-dioxane:water) and tested using a rapamycin standard, whichproduces peaks for the rapamycin isomers (B and C) and seco-rapamycinpeaks. In order to determine the amount of rapamycin (μg) content in thestent coating, at least five rapamycin standard solutions were run andan average total peak area for the B and C isomers were determined(A_(standard)) in addition to the purity of the standards (purity factor(PF)). Next, test samples (ACN with rapamycin eluted from coated stents)were run on the HPLC and average total peak areas for the B and Cisomers were determined (A_(test)). W_(standard) is the weight of therapamycin reference standard in mg and DF is the dilution factor of thetest sample. Following HPLC and rapamycin peak analysis, the followingcalculation was performed to determine the amount of rapamycin (μg)eluted from the stent:((A_(test)×W_(standard)×DF×PF)/A_(standard))Purity of the eluted rapamycin was determined by determining the peakarea of the impurity peak(s) for the test samples (A_(impurity-test))and calculating based on this formula (percent impurity):((A_(impurity-test)×100)/A_(standard))Rapamycin Analysis—Drug Dissolusion Method

Drug dissolution (elution of rapamycin from the coating) was performedusing a Sotax CE7 Smart/Agilent 8453 UV Spectrophotometer DissolutionSystem. The following parameters were applied for the assessing theamount of rapamycin eluted from the coated stents.

-   Dissolution Medium: 2% SLS-   Temperature: 37° C.-   Flowrate: 16 ml/min-   Sampling Interval: 15 minutes (1^(st) 3 hours)-   Sampling Interval: 60 minutes (after first 3 hours-24 hours)-   12 mm Cell (stents are placed here) 7 individual cells per run 279,    or 292 nm Rapamycin peak used for calculations

Example 7

Heparin coating compositions containing pBMA/photo-PVP/photo-heparinmixtures (samples 7-C1 to 7-C14) or pBMA/photo-heparin mixtures (samples7-B1 to 7-B8) in ternary or binary solvent systems were spray coatedonto stents having a pre-coating containing all of the following coatedlayers: (I) silane layer, (II) Parylene™ layer, (III)pBMA/pEVA/rapamycin layer, and (IV) pBMA layer (as described herein).

The heparin compositions were spray coated using the ultrasonic coatingapparatus onto pre-coated stents to provide a target coating weight (theheparin-containing layer) of approximately 100 μg, and within the rangeof 50 μg to 150 μg.

The concentrations of pBMA, photo-PVP, and photo-heparin in theheparin-containing layer, as well as the percentages of THF, EPA, andH₂O for all of the coating compositions are described in Table 7.

Mixtures were disposed on stents using the spray coating techniquedescribed herein. In some samples the coated stents were subject toirradiation for 60 seconds at 1 mW/cm² using a 407 nm center wavelengthfilter (Edmund).

A mixture of pBMA/photo-PVP was used as a heparin activity control(samples 7-A1 and 7-A2). TABLE 7 Coating Composition Reagent (mg/mL)Heparin Sample photo- Photo- Solvent (%) activity No. pBMA PVP heparinTHF IPA H₂O (mU/cm²) 7-A1 5 2.5 (−) 90 10 (−) 4 7-A2 5 2.5 (−) 90 10 (−)4 7-B1 5 (−) 5 90 (−) 10 8 7-B2 5 (−) 5 90 (−) 10 13 7-B3 2.5 (−) 5 90(−) 10 7 7-B4 2.5 (−) 5 90 (−) 10 12 7-B5 5 (−) 5 90 (−) 10 9 7-B6 5 (−)5 90 (−) 10 10 7-B7 2.5 (−) 2.5 90 (−) 10 6 7-B8 2.5 (−) 2.5 90 (−) 1011 7-C1 5 1.25 2.5 65 10 25 64 7-C2 5 1.25 2.5 65 10 25 67 7-C3 5 0.31251.25 80 5 15 66 7-C4 5 0.3125 1.25 80 5 15 67 7-C5 5 0.3125 0.625 80 515 67 7-C6 5 0.3125 0.625 80 5 15 64 7-C7 2.25 2.5 4.5 72 18 10 78 7-C82.25 2.5 4.5 72 18 10 66 7-C9 2.5 1.25 1.25 70 10 20 62 7-C10 2.5 1.251.25 70 10 20 70 7-C11 2.5 0.94 2.5 75 7.5 17.5 59 7-C12 2.5 0.94 2.5 757.5 17.5 73 7-C13 2.5 0.3125 1.25 80 5 15 60 7-C14 2.5 0.3125 1.25 80 515 61

High levels of heparin activity were shown on the surface of stentscoated with pBMA/photo-PVP/photo-heparin mixtures. Stents coated withpBMA/photo-heparin mixtures (no photo-PVP) had very low levels ofheparin activity.

Example 8

Various heparin coating compositions containingpBMA/photo-PVP/photo-heparin mixtures in ternary solvent systems havingvarying THF/IPA/H₂O ratios (samples J-K) were spray coated ontopre-coated stents. The pre-coated stents had a pre-coating containingall of the following coated layers: (I) silane layer (II) Parylene™layer, (II) pBMA/pEVA/rapamycin layer, and (IV) pBMA layer, as indicatedabove. One sample utilized an IPA/H₂O binary solvent system.

The compositions were spray coated onto the stents to provide a coatingweight (for the heparin-containing layer) of approximately 100 μg, andin the range of 50 μg to 150 μg.

The concentrations of pBMA, photo-PVP, and photo-heparin, as well as thepercentages of THF, IPA, and H₂O for all of the coating compositions aredescribed in Table 8.

Mixtures were disposed on stents using the spray coating techniquedescribed herein. In some samples the coated stents were subject toirradiation for 60 seconds at 1 mW/cm² using a 407 nm center wavelengthfilter (Edmund). TABLE 8 Coating Composition Reagent (mg/mL) HeparinSample photo- Photo- Solvent (%) activity No. pBMA PVP heparin THF IPAH₂O (mU/cm²) 8-A1 5 0.625 0.625 (−) 95 5 18 8-A2 5 0.625 0.625 (−) 95 520 8-A3 5 0.625 0.625 (−) 95 5 11 8-B1 5 0.3125 0.625 80 5 15 31 8-B2 50.3125 0.625 80 5 15 35 8-B3 5 0.3125 0.625 80 5 15 35 8-C1 5 0.31250.625 70 15 15 34 8-C2 5 0.3125 0.625 70 15 15 37 8-D1 5 0.3125 0.625 6025 15 40 8-D2 5 0.3125 0.625 60 25 15 39 8-E1 5 0.3125 0.625 50 35 15 348-E2 5 0.3125 0.625 50 35 15 32 8-F1 5 0.3125 0.625 40 50 10 25 8-G2 50.3125 0.625 40 50 10 25 8-G3 5 0.3125 0.625 40 50 10 24 8-G4 5 0.31250.625 40 50 10 25 8-H1 5 0.3125 0.625 30 65 5 17 8-H2 5 0.3125 0.625 3065 5 16 8-I1 5 0.3125 0.625 20 75 5 16 8-I2 5 0.3125 0.625 20 75 5 18

As shown in table 8, heparin activity improved upon increasing amountsof THF or H₂O in the coating compositions.

Example 9

Stents coated with pBMA/photo-PVP/photo-heparin compositions indifferent binary or ternary solvent systems were tested for durabilityusing expansion testing, or expansion in combination with incubation inserum. In some cases the pBMA/photo-PVP/photo-heparin compositions wereprepared by including a photoactivatable crosslinking agent(4,5-bis(4-benzoylphenylmethyleneoxy)benzene-1,3-disulfonic aciddipotassium salt (DBDS), as described in U.S. Pat. No. 6,669,994). Theheparin compositions were coated on stents having a pre-coatingcontaining all of the following coated layers: (I) silane layer (II)Parylene™ layer, (III) pBMA/pEVA/rapamycin layer, and (IV) pBMA layer,as indicated above.

The amounts of components present in the heparin-containing compositionsis indicated in Table 9. TABLE 9 Coating Composition Reagent (mg/mL)Photo- photo- photo- X- Solvent (%) Sample set pBMA PVP heparin linkerTHF IPA H₂O 9-(A1-A9) 5 0.625 0.625 (−) (−) 98.75 1.25 9-(B1-B8) 5 0.6250.625 0.1875 (−) 95 5 9-(C1-C9) 5 0.625 0.625 (−) 80 5 15 9-(D1-D9) 50.3125 1.25 (−) 80 5 15

In order to provide an equal amount of coating composition to thestents, sample sets 9-(A1-A9) and 9-(B1-B8) were subject to 75 cycles ofspray coating, whereas sample sets 9-(C1-C9) and 9-(B1-B8) were subjectto 160 cycles.

Sets A, B, C, and D of coated stents were then subject to durabilitytesting. In one aspect durability testing was carried out by mechanicalchallenge by a balloon expansion process. The balloon expansion processwas performed by hand crimping the stent down on an appropriately sizedballoon in a 37° C. water bath and then expanding the balloon. In somecases stents were placed in Bovine Serum (Invitrogen Life Technologies)contained in a glass vial and shaken at 37° C. for the period of time asindicated in Table 10. TABLE 10 Heparin Activity (mU/cm) 9- 9- SampleNos. (A1-A9) 9-(B1-B8) 9-(C1-C9) (D1-D9) 1 - control 11 15 35 41 2 -control 14 13 29 33 3 - balloon expanded 10 12 34 35 4 - balloonexpanded 10 9 36 32 5 - balloon expanded + 9 10 31 33 1 day serumtreatment 6 - balloon expanded + 5 7 30 36 2 days serum treatment 7 -balloon expanded + 4 7 30 29 3 days serum treatment 8 - balloonexpanded + 10 11 33 38 1 day serum treatment + detergent wash 9 -balloon expanded + 11 (—) 33 28 1 day serum treatment + detergent wash

As seen in the examples, sets 9-(C1-C9) and 9-(D1-D9) provided stentsthat maintained excellent heparin activity after mechanical challenge.Sets 9-(C1-C9) and 9-(D1-D9) were prepared with a solvent system thatincluded THF.

Example 10

The content and quality of rapamycin from stents having apBMA/photo-PVP/photo-heparin and pBMA/photo-heparin coatings weretested. These heparin-containing coatings were formed on stents having apre-coating containing the following coated layers: (I) silane layer(II) Parylene™ layer, (III) pBMA/pEVA/rapamycin layer, and (IV) pBMAlayer, as indicated above.

The pBMA/pEVA/rapamycin layer contained approximately 125-140 μg ofrapamycin and in a total layer weight of about 450-510 μg.

The heparin coatings were spray coated onto the stents to provide acoating weight (for the heparin-containing layer) of approximately 100μg, and in the range of 50 μg to 150 μg.

The coatings were dissolved in acetonitrile and rapamycin was analyzedfrom the dissolved coatings using the HPLC procedures described herein.In this Example, rapamycin was not eluted from the coatings but rather,the coatings were dissolved and rapamycin analyzed from the dissolvedcoatings. TABLE 11 Coating Composition % Reagent (mg/mL) Re- Samplephoto- photo- Solvent (%) cov- % No. PBMA PVP heparin THF IPA H₂O eryArea 10-A1 5 1.25 2.5 65 10 25 83 97.9 10-B1 2.5 1.25 1.25 70 10 20 8697.7 10-C1 2.5 0.94 2.5 75 7.5 17.5 82 96.3 10-D1 2.25 4.5 2.5 72 18 1082 96.3 10-E1 5 (−) 2.5 90 (−) 10 82 96.1 10-F1 2.5 (−) 2.5 90 (−) 10 8297.2 10-G1 2.5 (−) 5 90 (−) 10 83 96.4 10-H1 5 (−) 5 90 (−) 10 83 97.910-I1 5 0.3125 0.625 80 5 15 80 94.7 10-J1 5 0.3125 1.25 80 5 15 83 96.610-K1 2.5 0.3125 1.25 80 5 15 80 97.6 Cont 1 (−) (−) (−) (−) (−) (−) 9099.2 Cont 2 (−) (−) (−) (−) (−) (−) 90 98 10-B2 2.5 1.25 1.25 70 10 2082 96.3 10-C2 2.5 0.94 2.5 75 7.5 17.5 85 95.8 10-D2 2.25 4.5 2.5 72 1810 82 96.7 10-E2 5 (−) 2.5 90 (−) 10 80 96.8 10-F2 2.5 (−) 2.5 90 (−) 1082 97.2 10-G2 2.5 (−) 5 90 (−) 10 79 98 10-H2 5 (−) 5 90 (−) 10 83 97.410-I2 5 0.3125 0.625 80 5 15 80 97.7 10-J2 5 0.3125 1.25 80 5 15 85 96.610-K2 2.5 0.3125 1.25 80 5 15 82 96.5

As seen from Table 11 rapamycin was recovered from the coatings at agood recovery percentage. In control samples (nophoto-heparin-containing layer) 90% of the drug was recovered from thestent. None of the stents tested displayed a loss of rapamycin recoveryof greater than 12.3% ([Cont 1-(10-12)]/Cont 1; 90-79/90). None of thestents having a pBMA/photo-heparin/photo-PVP coating displayed a loss ofrapamycin recovery of greater than 11.2% ([Cont 1-(10-12)]/Cont 1). Onaverage the loss of rapamycin recovery for stents having apBMA/photo-heparin/photo-PVP layer was 8.4% ([90-82.46(ave)]/90).

As shown by chromatography analysis, the rapamycin recovered from thestents having a photo-heparin-containing layer, on average, had a veryhigh level of purity. For control samples the % area as assessed by HPLCanalysis was average of 98.6%. For stents having the pBMA/photo-heparinlayer the loss in purity was only in the range of 0.61% to 2.5%. Forstents having the pBMA/photo-heparin layer the loss in purity was onlyin the range of 0.61% to 3.95%.

Example 11

The elution of rapamycin from stents either having or lacking a pBMAintermediate layer in combination with the pBMA/photo-PVP/photo-heparinlayer were tested. Heparin-containing coatings were formed on stentshaving a pre-coating containing the following coated layers: (I) silanelayer (II) Parylene™ layer, (III) pBMA/pEVA/rapamycin layer, and, whenindicated, a (IV) pBMA layer.

This coating was applied and the drug layer was formed having an amountof rapamycin in the drug layer in the range of 153-169 μg.

Various amounts of heparin composition were deposited on the stent. Theheparin coatings were spray coated onto the stents to provide atheoretical amount of heparin as indicated in Table 12.

Rapamycin was eluted by a Sotax method (described herein) over a periodof 24 hours. After 24 hours the amount of rapamycin eluted from thestent (and dissolved in solution was determined). TABLE 12 pBMA HeparinCoating Composition % Sample inter. Reagent (mg/mL) Solvent (%) μg rapaNo. Coat pBMA photo-PVP Photo-heparin THF IPA H₂O heparin dissolv. 11-ANo 5 1.25 2.5 65 10 25 18 82 11-B Yes 5 1.25 2.5 65 10 25 16 60 11-C No5 0.3125 1.25 80 5 15 13 79 11-D Yes 5 0.3125 1.25 80 5 15 10 52 11-E No(−) (−) (−) (−) (−) (−) 0 83 11-F Yes (−) (−) (−) (−) (−) (−) 0 52

As seen from the control examples in Table 12 the presence of the pBMAintermediate layer caused a decrease in the amount of rapamycin elutedfrom the coated stents. However, the presence of the heparin-containinglayer did not significantly affect the amount of rapamycin eluted fromthe coated stents.

Example 12

The content and quality of rapamycin in present in coatings from stentshaving heparin-containing coatings was tested following irradiation ofthe stents with UV through various filters. This test was performed todetermine the effect of different types of filters on drug elution.Filter A (Edmunds Optics, 407 nm maximum transmittance), Filter B (324nm cut-off filter), Filter C (BG-38, 470 nm maximum transmittance), andFilter D (Opto-Sigma 077-3550; colored Glass filter maximumtransmittance at 500 nm), and Filter E (Opto-Sigma 077-3440 ColoredGlass filter; maximum transmittance 400 nm) were used. Filters D and Ehave particularly low transmittance below 300 nm.

The stents were prepared, as indicated above, were (I) silane-treatedand had a (II) Parylene™ base layer, (III) a pBMA/pEVA/rapamycin layer,(IV) a pBMA layer, and (V) a pBMA/photo-heparin/photo-PVP (as indicatedin Table 13). In the samples, the pBMA/pEVA/rapamycin was formed havingan amount of rapamycin in the range of 115-145 μg.

The coatings were dissolved in acetonitrile and rapamycin was analyzedfrom the dissolved coatings using the HPLC procedures described herein.

The stents were irradiated using the following conditions:

12-A1: Standard filter, UV 60 seconds at 0.8-1.2 mW/cm²

12-A2: Standard filter, UV 30 seconds at 0.8-1.2 mW/cm²

12-B1: 324 nm filter, UV 60 seconds at 2.0 mW/cm²

12-B2: 324 nm filter, UV 30 seconds at 2.0 mW/cm²

12-C1: BG-38 filter, UV 60 seconds at 1 mW/cm²

12-C2: BG-38 filter, UV 30 seconds at 1 mW/cm²

12-C3: BG-38 filter, UV 15 seconds at 1 mW/cm²

12-D1: Opto-Sigma 077-3550, UV 60 seconds at 1.1 mW/cm²

12-D2: Opto-Sigma 077-3550, UV 30 seconds at 1.1 mW/cm²

12-E1: Opto-Sigma 077-3440, UV 30 seconds at 1.1 mW/cm²

Measurement are made from a radiometer from International Light with a335 filter (filter out UV outside of 330-340 nm wavelength)

The results from the samples shows the average percent recovery from agroup of stents prepared and irradiated in the same manner. TABLE 13Heparin Coating Composition Reagent (mg/mL) Filter/ photo- Photo-Solvent (%) % UV pBMA PVP heparin THF IPA H₂O Recovery 12-A1 5 0.6250.625 50 40 10 79.9 12-A2 5 0.625 0.625 50 40 10 85.4 12-B1 5 0.6250.625 50 40 10 85.0 12-B2 5 0.625 0.625 50 40 10 84.4 (−) 5 0.625 0.62550 40 10 85.6 12-C1 5 0.625 0.625 50 40 10 84.1 12-C2 5 0.625 0.625 5040 10 85.6 12-C1 5 0.3125 0.625 88.75 0.25 11 89.9 12-C2 5 0.3125 0.62588.75 0.25 11 87.1 12-C3 5 0.3125 0.625 88.75 0.25 11 84.5 12-D1 50.3125 0.625 88.75 0.25 11 78.1 12-D2 5 0.3125 0.625 88.75 0.25 11 81.112-E1 5 0.3125 0.625 88.75 0.25 11 83.0 (−) (−) (−) (−) (−) (−) (−) 83.9

Example 13

Heparin activity was tested on the surface of stents that were coatedwith various heparin-containing compositions, wherein the compositionswere subject to irradiation either before or after the compositions werespray coated onto the surface of the stents.

The stents prepared, as indicated above, were (I) silane-treated and hada (II) Parylene™ base layer, (III) a pBMA/pEVA/rapamycin layer, (IV) apBMA layer, and (V) a pBMA/photo-heparin/photo-PVP (as indicated inTable 14).

Pre-irradiation was performed by subjecting the heparin-containingcomposition to UV (non-filtered) for 2-4 times irradiation for 99seconds per time.

Post-irradiation was performed by subjecting stents to 60 seconds UVwith standard filter. TABLE 14 Heparin Coating Composition HeparinSample Reagent (mg/mL) Solvent (%) Pre- Post- Activity No. pBMAphoto-PVP photo-heparin THF IPA H₂O photo photo MU/cm² 13-A 10 (−) (−)*90 (−) 10 (+) (−) 9 13-B 5 0.625 (−)** 50 40 10 (+) (−) 7 13-C 5 0.625(−)** 50 40 10 (−) (−) 9 13-D 10 (−) 5 90 (−) 10 (−) (−) 4 13-E 5 0.6250.625 50 40 10 (−) (−) 3 13-F 10 (−) 5 90 (−) 10 (+) (−) 5 13-G 5 0.6250.625 50 40 10 (+) (−) 30 13-H 5 0.625 0.625 50 40 10 (+) (−) 33 13-I 50.625 0.625 50 40 10 (−) (+) 30*Na-heparin @ 5 mg/mL was substituted for photo-heparin**Na-heparin @ 0.625 mg/mL was substituted for photo-heparin

These results show that biocompatible layer having excellent heparinactivity can be formed by pre-irradiating the heparin coatingcomposition prior to depositing the composition on the surface of thecoated article. Pre-irradiation gave the same heparin activity as stentshaving compositions that were post-irradiated.

Example 14

Heparin activity was tested on the surface of stents having a coating ofpolylactic acid with a rapamycin analog that were coated with variousheparin-containing compositions, wherein the compositions were subjectto irradiation after the compositions were spray coated (or 5 solutioncoated where indicated) onto the surface of the stents. Irradiation wasperformed by subjecting the heparin-containing composition to UV(filtered using an Edmund 407 filter) for 60 seconds.

The photo-crosslinker (Compound IV; TBBE) was used at a concentration inthe range of 1-5 mg/mL. PLA was used at a concentration in a range of1-10 mg/mL. Top coats of photo-heparin (alone) were applied in water ata concentration of 50 mg/mL. TABLE 15 Heparin Sample Coating ActivityNo. First Coat Second Coat MU/cm² 14-A1 Photo-PVP in solution UV(filtered) Photo-PVP/PLA/photo-heparin 42 UV (filtered) 14-A2 Photo-PVPin solution UV (filtered) Photo-PVP/PLA/photo-heparin 41 UV (filtered)14-B1 Photo-crosslinker spray (THF) UV Photo-heparin (THF/Water) 53(filtered) spray, UV (filtered) 14-B2 Photo-crosslinker spray (THF) UVPhoto-heparin (THF/Water) 45 (filtered) spray, UV (filtered) 14-C1Photo-crosslinker spray (THF) UV Photo-heparin (Water) spray, 12(filtered) UV (filtered) 14-C2 Photo-crosslinker spray (THF) UVPhoto-heparin (Water) spray, 11 (filtered) UV (filtered) 14-D1Photo-PVP/PLA/photo-heparin spray Photo-heparin (THF/Water) 45 UV(filtered) spray, UV (filtered) 14-D2 Photo-PVP/PLA/photo-heparin sprayPhoto-heparin (THF/Water) 46 UV (filtered) spray, UV (filtered) 14-E1Photo-PVP/PLA/photo-heparin spray (−) 46 UV (filtered) 14-E2Photo-PVP/PLA/photo-heparin spray (−) 46 UV (filtered)

Similar to previous results, these results also show that biocompatiblelayer having excellent heparin activity can be formed by pre-irradiatingthe heparin coating composition prior to depositing the composition onthe surface of the coated article. These results also show thatbiocompatible layer having excellent heparin activity can be formedusing on a biodegradable layer. These results also show that a non-watersoluble photo-crosslinker can be used to promote the formation of alayer with heparin activity, wherein the photo-heparin is applied in abinary solvent system.

Example 15

Heparin activity was tested on the surface of stents that were coatedwith various heparin-containing compositions, wherein the compositionswere subject to irradiation before the compositions (pre-irradiation)were spray coated onto the surface of the stents.

The stents were prepared, as indicated above, were (I) silane-treatedand had a (II) Parylene™ base layer, (III) a pBMA/pEVA/rapamycin layer,(IV) a pBMA layer, and (V) a pBMA/photo-heparin/photo-PVP (as indicatedin Table 16).

Stents were subject to mechanical testing as described in Example 9.

Pre-irradiation was performed by subjecting the heparin-containingcomposition to UV (non-filtered) for 4 times irradiation for 99 secondsper time. Using a Dymax light without the filter (greater than 25mU/cm²) TABLE 16 Heparin Heparin Coating Composition Activity SampleReagent (mg/mL) Solvent (%) MU/cm² No. pBMA photo-PVP photo-heparin THFIPA H₂O Expanded Wash (mean) 15-A 5 0.625 0.625 50 40 10 (+) Plasma 2215-B 5 0.625 0.625 50 40 10 (−) PBS 37 15-C 5 0.1 0.1 <90* <10* <1 (+)Plasma 5 15-D 5 0.1 0.1 <90* <10* <1 (−) PBS 6 15-E 5 0.5 0.1 <90* <10*<1 (+) Plasma 5 15-F 5 0.5 0.1 <90* <10* <1 (−) PBS 7 15-G 5 0.1 0.5  79.2   19.8 <1 (+) Plasma 26 15-H 5 0.1 0.5   79.2   19.8 <1 (−) PBS29 15-I 5 0.5 0.5   79.2   19.8 <1 (+) Plasma 39 15-J 5 0.5 0.5   79.2  19.8 <1 (−) PBS 34 15-K 20 0.4 0.4   79.2   19.8 <1 (+) Plasma 4 15-L20 0.4 0.4   79.2   19.8 <1 (−) PBS 7*THF and IPA were lower than the indicated values to allow for a smallamount of water in the solvent system

These results show that optimal durability and heparin activity (15G-I)was seen when the amount of water was reduced to very low concentrationsin the solvent (<1%). This allowed for higher concentrations of pBMA inthe mixture, which provided excellent durability. Low concentrations ofphoto-heparin in Samples 15C-F were believed to cause the low heparinactivity.

1. A method for providing a biocompatible coating to a surface of amedical article, comprising the steps of: (a) irradiating a compositioncomprising (i) a first polymer, (ii) photoreactive groups, and (iii) abiocompatible agent selected from the group consisting ofpolysaccharides and polypeptides, wherein irradiating activates thephotoreactive groups; and (b) after step (a), disposing the irradiatedcomposition on the medical article.
 2. The method of claim 1 where, inthe step of irradiating, the first polymer comprises a hydrophobicpolymer.
 3. The method of claim 2 where, in the step of irradiating, thefirst polymer is selected from the group consisting ofpoly(alkyl(meth)acrylates).
 4. The method of claim 3 where, in the stepof irradiating, the first polymer is poly(butyl(meth)acrylate).
 5. Themethod of claim 1 where, in the step of irradiating, the first polymeris present in the composition in the range of 1-20 mg/mL.
 6. The methodof claim 1 where, in the step of irradiating, the composition comprisesa polysaccharide selected from the group consisting of heparin,hyaluronic acid, chondroitin, keratan, and dermatan.
 7. The method ofclaim 1 where, in the step of irradiating, the composition comprises apolypeptide selected from the group consisting of fibronectin, laminin,collagen, elastin, vitronectin, tenascin, fibrinogen, albumin,thrombospondin, osteopontin, von Willibrand Factor, bone sialoprotein,and active domains thereof.
 8. The method of claim 1 where, in the stepof irradiating, biocompatible agent is present in the composition in therange of 0.1 mg/mL -10.0 mg/mL
 9. The method of claim 1 where, in thestep of irradiating, the photoreactive groups are pendent from thebiocompatible agent.
 10. The method of claim 1 where, in the step ofirradiating, the composition further comprises a component selected fromthe group consisting of polyvinylpyrrolidone, polyethylene glycol,polyethylene glycol sulfonates, fatty quaternary amines, fattysulfonates, fatty acids, dextran, dextrin, and cyclodextrin.
 11. Themethod of claim 10 where, in the step of irradiating, the component ispresent in the composition in the range of 0.1 mg/mL to 2.5 mg/mL. 12.The method of claim 10 where, in the step of irradiating, the componentcomprises polyvinylpyrrolidone.
 13. The method of claim 10 where, in thestep of irradiating, photoreactive groups are pendent from the componentselected from the group consisting of polyvinylpyrrolidone, polyethyleneglycol, polyethylene glycol sulfonates, fatty quaternary amines, fattysulfonates, fatty acids, dextran, dextrin, and cyclodextrin.
 14. Themethod of claim 13 where, in the step of irradiating, the photoreactivegroups are pendent from both heparin and poly(vinylpyrrolidone).
 15. Themethod of claim 1 where, in the step of irradiating, the compositioncomprises a first liquid selected from THF or acetone.
 16. The method ofclaim 15 where, in the step of irradiating, the composition comprises asecond liquid selected from diethylene glycol, methanol, ethanol,n-propanol, isopropanol (IPA), n-butanol, chloroform, methylenechloride, 2-pyrrolidone, polyethylene glycol, propylene glycol,1,4-butanediol, glycerol, triethanolamine, propionic acid, and aceticacid.
 17. The method of claim 1 where, in step (b), the irradiatedcomposition is disposed on the medical article comprising anintermediate coated layer comprising a second polymer.
 18. The method ofclaim 17, where, in the step of irradiating, the second polymer isdifferent than the first polymer.
 19. The method of claim 18, where, inthe step of irradiating, the second polymer and the first polymer arehydrophobic.
 20. The method of claim 17, where, in the step ofirradiating, the second polymer is selected from the group consisting ofpoly(alkyl(meth)acrylates), and poly(aromatic(meth)acrylates),poly(ethylene-co-vinyl acetate), diolefin derived non-aromatic polymersand copolymers, and poly(vinylpyrrolidone).
 21. The method of claim 1where, in step (b), the medical article comprises an intraluminalprosthesis.
 22. The method of claim 21 where, in step (b), theintraluminal prosthesis is self-expanding.
 23. The method of claim 22where, in step (b), the intraluminal prosthesis comprises a metal alloy.24. The method of claim 23 where, in step (b), wherein the intraluminalprosthesis comprises nitinol.
 25. The method of claim 23 where, in step(b), the composition is disposed on a portion of the intraluminalprosthesis that will come in contact with bodily fluids.
 26. The methodof claim 1, in step (b), the composition is disposed on a medicalarticle selected from the group consisting of diagnostic articles andsensors.
 27. A method for preparing a medical article having abiocompatible surface, comprising the steps of: (a) irradiating acomposition comprising a biocompatible agent, photoreactive groups, ahydrophobic polymer, and a component selected from the group consistingof polyvinylpyrrolidone, polyethylene glycol, polyethylene glycolsulfonates, fatty quaternary amines, fatty sulfonates, fatty acids,dextran, dextrin, and cyclodextrin, to activate the photoreactivegroups; (b) after step (a), disposing the irradiated composition on amedical article.
 28. A method for preparing a medical article having asurface having heparin or collagen activity comprising the steps of: (a)irradiating a composition comprising heparin or collagen, photoreactivegroups, a first polymer that is hydrophobic, and a second polymer thatis different than the first polymer; (b) after step (a), disposing theirradiated composition on a medical article.